European Cooperation in Science and Technology …ESSEM ...

UV RADIATION AND LIFE

Authors: Zenobia Lity ńska, Alois W. Schmalwieser, Alkiviadis Bais, Karel Ettler, Julian Gröbner, Peter Köpke, Janusz Krzy ścin, Peter den Outer, Jean Verdebout, Gaetano Zipoli and Julita Biszczuk-Jakubowska

COST Action 726 Table of content

1. Introduction...... 3 2. Solar UV radiation ...... 5 2.1. Factors influencing UV radiation ...... 5 2.2. UV Measurements ...... 10 2.3. UV modelling...... 12 2.4. Geographical distribution and temporal variability of UV radiation in Europe...... 15 3. Biologically effective radiation ...... 21 3.1. Biological effects of UV radiation on human body ...... 22 3.2. UV Radiation and Animals ...... 27 3.3. Micro-organisms and UV radiation...... 30 3.4. UV radiation and Plants ...... 33 3.5. UV and aquatic systems ...... 36 4. Expectations for the future...... 40 Appendix A: Reference Institutions in the COST726 Countries...... 43 Appendix B: List of www pages with UV information ...... 48 Appendix C: List of reference publications...... 49

2 1. Introduction

The UV radiation plays an essential role in many processes in the biosphere, including the influence on the human body, and may be very harmful if UV exposure exceeds certain limits. The main results achieved in Action 726 are published in the Final Report and in the e-Atlas, which contains the elaborated UV maps for Europe for about 50 years and a sample of long-term spectral UV data. The knowledge of the ozone and UV changes has expanded considerably since the “ozone hole” discovery in the early 1980s and the subsequent establishment of the Ozone Convention in 1985, and the Montreal Protocol in 1987. The awareness of the potential ozone depletion threat and the resulting increase in the UV radiation reaching the Earth surface stimulated the world-wide multidisciplinary research on UV radiation transfer in the atmosphere and its potential influence on the Earth’s ecosystems. The correlation between the ozone and UV changes and the climate changes has been recognised. The COST Action 726 “Long term changes and climatology of UV radiation over Europe” was established in 2004. Its main objective is to advance the understanding of the UV radiation distribution under various meteorological conditions, in order to determine the UV radiation climatology, and to assess the long-term UV changes over Europe, starting in the 1950s. The main objectives of this booklet are to show the importance of the scientific results of Action 726 for the European community, to increase the awareness of the potential threat of UV radiation to human health, and to urge people to use appropriate protective measures. This booklet initially provides basic information on solar UV radiation reaching the Earth surface (section 2.1). Sections 2.2 and 2.3 describe the measurements of UV and the methods of retrieving the UV by modelling and reconstruction. The main results of the Action, i.e. the geographical distribution and temporal variability of UV radiation in Europe, are presented in section 2.4. Chapter 3 describes the biologically effective UV radiation and its influence on the human body, animals, micro organisms, plants and the aquatic biosphere. Chapter 4 presents the current expectations on

3 future UV changes. Appendixes A, B, C show the European dimension of the COST Action 726 and contain useful web addresses and references. This booklet is addressed to the broad European community to help further the understanding of the UV radiation impact on the Earth surface, with its potential positive and harmful influences, and to stress the necessity of using protective measures. In particular, we address this booklet to journalists and school teachers. This booklet was written by lead-authors but is a result of the collective efforts of the Management Committee and the four Working Group leaders and members of the 22 EC COST countries and one non-COST country, for details see Appendix A. The COST Action web site: www.cost726.org has been built and is being managed by Dr Alois Schmalwieser from the University of Veterinary Medicine in Vienna, Austria. The web site contains all important information on the Action and main research results including the elaborated UV climatic data for Europe.

4 2. Solar UV radiation

The spectrum of solar radiation consists of ultraviolet radiation - UV (100- 400nm), the visible radiation-VS (400-780nm) and the infrared radiation-IR (780- 3500nm). The UV radiation is a small fraction of the total radiant solar energy, but even only partially reaching the Earth surface it may produce detrimental effects on ecosystems and degrading effects on materials. The most energetic part of the spectrum, the UV-C (100-280nm) radiation, is absorbed effectively by oxygen, ozone and nitrogen molecules in the upper atmosphere. The UV-B (280-315nm) radiation is strongly absorbed by the ozone layer in the stratosphere and by the ozone in the troposphere, so that only a small fraction of its energy reaches the Earth surface, strongly depending on the ozone amount. The UV-B is of great biological importance because photons in this spectral region may damage skin, DNA molecules and some proteins of living organisms. On the other hand UV-B is essential for the synthesis of vitamin D in the human body. The UV-A (315-400nm) radiation is hardly absorbed by ozone, so its largest part reaches the surface, contributing to some biological effects like photoaging, photoprotection and photorepair. During its propagation through the atmosphere, the UV radiation is absorbed and scattered by ozone, air pollutants in the troposphere, clouds and aerosols. Part of it, is also reflected by the Earth surface.

2.1. Factors influencing UV radiation

The spectrum of UV irradiance at the Earth surface is determined by that at the top of the atmosphere. Other factors that drive the intensity and angular distribution of UV sky radiance at the surface are divided into 2 classes: geometrical and atmospheric. The geometrical factors comprise the distance between the Earth and sun and solar zenith angle (SZA). The effects from these factors can be calculated using astronomical formulas. Atmospheric factors include constituents that absorb and scatter radiation during its propagation

5 towards the Earth surface. The absorbing species are: ozone, nitrogen dioxide, sulphur dioxide, and absorbing aerosols. The scattering species include air molecules, clouds, aerosols, and the ground (snow, ice, vegetation, sand, etc.) a) The Solar Spectrum The solar spectrum is derived from space-based measurements. The solar spectrum at the top of the atmosphere (~ 100km above surface) is used as input for radiative transfer model calculations. Both direct and indirect effects of the solar activity are recognized. Direct effects are related to small oscillations (<1%) in the UV-A and UV-B part of solar spectrum forced by the 11-year solar activity cycle. Larger effects occur in the UV-C part of the spectrum. Indirect effects are due to changes in the production of stratospheric ozone. During solar maxima, proportionally more UV-C radiation enters the top of the atmosphere triggering intensive production of ozone in the upper stratosphere. This increase in ozone, changes only slightly the amount of UV-B radiation reaching the Earth surface. b) Earth-Sun Distance

The Earth is closest to the sun in early January and farthest from the sun in early July because of its elliptical orbit around the sun. The difference between the January maximum and July minimum of the solar radiation intensity is approximately 7% regardless of wavelength. This difference decreases slightly the ratio between summer UV maximum and winter UV minimum in the Northern Hemisphere but increases this ratio in the Southern Hemisphere, to the reversal of the seasons. c) Solar Zenith Angle

Surface UV irradiance measured on a horizontal surface decreases with the sun approaching the horizon (increasing SZA). There are two reasons for such a decrease: Firstly, the solar irradiance falling on a horizontal plane at the Earth surface is weighted according to the cos(SZA). Secondly, the slant path-length of radiation through the atmosphere is proportional to 1/cos(SZA) leading to higher probability of absorption or scattering during its propagation through the atmosphere for higher SZA. For a particular site and time, the SZA is easily calculated using astronomical formulas. On days without clouds, the highest UV

6 irradiance during the course of the day is found at the time of the smallest SZA (local noon). The large difference between the spring/summer maxima and autumn/winter minima is mostly due to SZA effects as is illustrated in Fig.2.1.1. d) Absorption by Ozone and Other Gases

The negative correlation between the column amount of atmospheric ozone and UV-B radiation has been well documented. It has been found that 1% decrease (or increase) of stratospheric ozone induces ~1.1% increase (or decrease) in erythemal UV radiation, i.e., UV radiation integrated over the whole UV spectrum with a wavelength dependent weight proportional to the sensitivity of human skin to UV radiation induced erythema. Total ozone in the extratropical regions of the northern hemisphere shows a seasonal pattern with maximum in spring and minimum in late autumn. For a fixed SZA, this pattern induces smaller UV intensity in spring than in other seasons. However, with respect to daily doses of UV radiation, the changes due to the diurnal changes in SZA prevail over the seasonal ozone changes. Total ozone at mid- and high-latitudes exhibits large day-to-day variations driven mostly by dynamical processes, which are especially pronounced in winter/spring seasons. Several UV absorbing gases resulting from anthropogenic activity reside in the troposphere. These gases include O 3, NO 2, and SO 2. The column amount of these trace gases is not high enough to induce substantial changes over wider areas. However, in extreme cases or near emission sources combined absorption by the pollution gases can reduce erythemal radiation by up to 10-

15%. Naturally occurring absorbers of UV-B radiation (SO 2 and NO 2) are significant only after large volcanic eruptions but their impact on radiation reaching the surface is generally short and not widespread. e) Scattering by Air Molecules

Scattering of solar radiation by air molecules (Rayleigh scattering) is approximately proportional to 1/ λ4, where λ denotes wavelength. Thus, in the UV region there is much stronger scattering than in the visible. Rayleigh scattering causes stronger attenuation in the UV-B region compared to UV-A.

7 f) Scattering and Absorption by Aerosols

Atmospheric aerosols are solid particles (sometimes additionally coated with liquid water or water-soluble acid) with diameter of less than 10 m that are suspended in the atmosphere. Atmospheric aerosols affect surface UV radiation through scattering and absorption processes. The combined effect of scattering and absorption on solar radiation is described by the aerosol optical depth (AOD). AOD data can be determined from ground-based measurements of the direct component of surface UV radiation and recently from space borne platforms. AOD values measured in the UV range at clean, high latitude sites approach a few hundredths, whereas at lower latitudes AOD varies between ~0.05 and 2.0. The upper values can appear in extreme cases in polluted urban areas. g) Scattering by Clouds

Clouds induce more dynamical variability in surface UV radiation than all other geophysical factors combined, as it is well illustrated in Fig. 2.1.1. Various cloud types affect differently the UV transmission through a cloud layer. Comparing to cloudless conditions thin clouds reduce the direct component of UV radiation reaching the Earth surface and enhance the diffuse component, thus the total irradiance (a sum of both components) is only slightly reduced. Thicker clouds allow only the diffuse component to reach the Earth surface and thus strongly reduce the UV irradiance. In average for Europe clouds reduce the UV radiation at the surface to 65% of the same atmospheric conditions, but without clouds. Under scattered cloud conditions surface UV radiation however can be enhanced for a short time, to values that are higher than for the same atmospheric conditions without clouds. This occurs when the line of sight from the sun is not obscured by a cloud but there are clouds near the Sun which reflect additional UV radiation to the receiver. h) Surface Albedo

Part of the irradiance received on a horizontal plane has previously been reflected from the ground elsewhere end has been scattered downwards again by the above present atmosphere. The total reflection of the atmosphere is around 30%.. For water and most land surfaces this surface reflection, the

8 albedo, is low (<5%) in the UV range. Spatial differences in land use (forest, pasturage, urban areas, etc.) have little effect on surface UV radiation if the terrain is not covered by snow. The albedo of fresh snow may be as high as 0.9 in the UV range, ageing (days) reduces the albedo to around 0.5. There have been several studies indicating a correlation between UV enhancement and snow depth. The enhancements of UV radiation vary significantly from site to site and can reach 40% over a plane terrain covered by fresh snow. Radiative transfer model calculations indicate that surface albedo can influence UV radiation measurements in the radius of a few tens of kilometres, the distance depending on wavelength and atmospheric conditions. i) Altitude Effects

Surface UV irradiance increases with altitude because there are less scattering and absorbing air molecules, ozone and aerosols above the receiver. This increase is mostly driven by an increase in the direct component of UV radiation. Moreover, anthropogenic gases that absorb UV radiation are often close to the surface. Most of them reside in the planetary boundary layer over industrial regions. Thus, the rate of increase of surface UV radiation per 1km of altitude varies between a few percent in clean environments to about 15% over heavily polluted areas.

5 daily doses clear sky heavy cloud

) mean doses -2 4 m ERYT 3

2 DAILY DOSE DAILY (KJ DOSE 1

0 Julian Day

0 30 60 90 120 150 180 210 240 270 300 330 360

Fig. 2.1 .1: Seasonal changes of daily erythemal doses measured at Belsk, Poland (51.84ºN, 20.79ºE, 179m AMSL), in the period 1976-2007.

9

2.2. UV Measurements

Solar UV measurements are obtained with special instruments that are only sensitive to the UV wavelength range. Due to the very low intensity of UV radiation with respect to the remaining solar radiation spectrum, the effective rejection of radiation from wavelengths outside the UV wavelength range becomes a fundamental criterion. This specification can be achieved with radiometers employing very high quality filters.

Another possibility is to use spectroradiometers which are able to measure radiation at individual wavelengths with very high spectral resolution covering a wide spectral range, including UV. While spectroradiometers provide the most accurate measure of solar ultraviolet radiation, the costs involved in their operation and maintenance are very high and therefore only few of these instruments are operated regularly at selected locations in Europe. The UV monitoring networks in Europe therefore consist of filter radiometers which provide continuous measurements of solar UV radiation during the whole year. The monitoring sites of each regional or national network are situated at strategic locations to provide representative measurements of UV radiation levels for each particular geographic region. Characteristic regions of interest are sites in or close to large cities, rural and mountainous regions, and seaside regions. It has been found that UV monitoring radiometers which are continuously exposed to UV radiation show degradation effects which can affect their performance. Therefore, regular corrective measures are necessary to guarantee UV measurements of a prescribed level of accuracy. Based on a recommendation of the World Meteorological Organisation (WMO), these network radiometers should be recalibrated annually, either through comparison with a reference radiometer, or at a central calibration facility. Several such facilities are available in Europe, which are traceable to the European UV calibration center at PMOD/WRC (Physikalisch Meteorologisches Observatorium Davos/World Radiation Center). This hierarchical traceability chain between the UV reference maintained at PMOD/WRC and the individual

10 field radiometers of a particular network ensures the comparability and homogeneity of the UV measurements performed in Europe. Large efforts have been undertaken to ascertain and improve the data quality through the application of common maintenance and calibration procedures. Furthermore, large-scale radiometer intercomparisons allow the direct comparison between radiometers deployed in different networks. The final goal of these quality assurance and calibration activities is to provide harmonized UV measurements with known quality on a European scale for scientists, public authorities and the general public. The dissemination is done either through public web-sites operated by national or regional organisations and authorities or through centralised databases, such as the European UV Database operated by the Finnish Meteorological Institute or the World Ozone and Ultraviolet Radiation Data Centre hosted at Environment Canada. In the period 2006-2008 three inter-comparison campaigns were organised in: Davos, Switzerland; Oslo, Norway; El Arenosilo, Spain. A Calibration Guide was also produced and published (see Appendix C).

Fig. 2.2.1: Calibration and Intercomparison of Erythemal Radiometers at PMOD/WRC, Davos, Switzerland, 28 July – 23 August 2006.

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2.3. UV modelling

Although solar UV radiation is measured at many locations over Europe, these are still too few to provide a representative European-wide picture due to the large variability of UV radiation induced by the highly variable atmospheric constituents. Other situations, where solar UV radiation is of interest but measured values do not exist, are the future and partly the past. For these cases modelling of UV irradiance is the only method to get the relevant information. Moreover, modelling is needed for the determination of UV radiation at the ground on the basis of satellite data, which is the only way to get UV data with high spatial resolution. Finally, modelling is the easiest way for sensitivity studies in a wide range of applications, such as UV radiation and human health or environmental influences. Thus modelling of UV radiation is very essential . The emission of the Sun is highly wavelength dependent and also the processes in the atmosphere. As a consequence, solar radiation at the Earth surface varies within the UV spectral interval in a range of more than one million, even for fixed atmospheric conditions. Thus modelling must be made spectrally. On the other hand, the effects imposed by UV radiation are also strongly wavelength dependent. Such a dependency is described by a spectral action spectrum seffect (λ) for a specific process (see chapter 3 for details). Thus the effective radiation for a specific process is given by spectrally integrated values

Eeffect , where the incident spectral irradiance E( λ) is weighted by seffect (λ). = (λ)⋅ (λ)⋅ λ Eeffect ∫ E seffect d If spectral values of UV radiation are known for specific atmospheric conditions, which need high effort for measuring but less for modelling, the effective irradiance for every action spectrum can be easily calculated. For modeling of the UV radiation at the ground, the radiative transfer equation has to be solved, which can not be done analytically. Thus different models have been developed for this purpose, with different quality and, as a consequence, with different computational effort. State of the art are one dimensional spectral multiple scattering models, which model the radiation field for one set of atmosphere conditions in the order of seconds or less. They divide the

12 atmosphere in thin layers with fixed properties and change these properties only vertically, which is the reason for their name. The models use algorithms, which determine the values of extinction and absorption coefficients for each layer, on the basis of the amount and the properties of the variable atmospheric constituents. These multiple scattering models calculate the radiation spectrally and thus can consider any biological weighting. The models calculate the radiation that is coming from a half sphere, the irradiance, on horizontal and also on tilted surfaces. These are the quantities that are needed to estimate the UV exposure of the human skin. The UV irradiance on a tilted surface may strongly differ to that on a horizontal receiver. To get UV irradiances on tilted surfaces from measurements, a very high effort is necessary. The reason is that, also for fixed atmospheric conditions, the irradiance changes with elevation and azimuth angles of the receiver and thus many measurements must be made to get the whole variability. In contrast, modelling of UV irradiance on tilted surfaces, like the human skin, is easy, as long as the actual atmospheric conditions are quantitatively available. For the human environment often artificial or natural shadows should be considered. This also can be modeled, using the radiance fields and taking into account sky obstructions. The UV models with highest quality are three dimensional. They consider variable optical properties not only vertically, but also horizontally. These models can calculate UV radiation fields e.g. for conditions with scattered clouds or with variable surface albedo, and also with sky obstructions. However, such models need very long computation times. Moreover, for actual conditions it is nearly impossible to get precise information for an atmospheric layer or a cloud field in all three dimensions, which is needed as input. Thus three dimensional models are very good for sensitivity studies, but not for the simulation of actual conditions or for the evaluation of measured UV radiation. Solar UV radiation at the ground depends on the irradiance of the extraterrestrial Sun, the Earth-Sun distance, the solar elevation which is responsible for the photons path length through the atmosphere, and on the scattering and absorption processes due to the atmospheric parameters, which are strongly wavelength dependent. If all these parameters are known for an actual case, all

13 radiation quantities can be modeled with high quality, since the mathematical radiative transfer codes have very low uncertainties. The parameter with the strongest influence is the solar elevation. It changes the radiation from darkness during night up to the high values at noon and is also responsible for the variability of UV irradiance with respect to geographical latitude and the day in the year. However, solar elevation can be accurately calculated for a specific location on Earth and time and thus exact values can be taken into account for modeling. The same holds for the Earth-Sun distance and, besides minor temporal variations, for the spectral extraterrestrial solar irradiance. The atmospheric and ground properties, however, are more or less variable and for an actual case often not all information is available that is needed for precise modeling. Thus, for an actual case, modeled UV irradiance will be uncertain by up to 20% for cloud free conditions. The factors which are influencing the UV radiation are discussed in chapter 2.1. The largest uncertainty in estimating the actual UV radiation is resulting from the clouds. To model the effect of clouds with a one dimensional model, often the cloud effects are taken into account by the cloud modification factor (CMF). This is the spectral ratio of the irradiance for cloudy conditions over the irradiance for a hypothetical atmosphere with the same conditions, but without clouds. The latter can easily be modelled, and the resulting cloud free irradiance can be modified to the irradiance for cloudy conditions by multiplication with the CMF. Especially highly variable is the effect due to scattered clouds. Here the cloud amount is important, but even more the position of the clouds relative to the Sun. Thus, CMFs derived from cloud amount describe only average cloud conditions. A suitable way to derive CMFs for actual conditions is to use a known effect of the clouds in the visible spectral range (CMF VIS ) and transfer the cloud effects to the UV. CMF VIS can be derived from solar global radiation measurements, which often are available. This method implicitly includes all effects from the actual clouds, such as optical thickness, amount and the position of clouds relative to the Sun. The transformation of CMF VIS to CMF UV depends on solar elevation, an effect which has to be taken into account For calculating the UV radiation different models exist (e.g. UVspec, Mystic, STAR), which are freely available.

14

2.4. Geographical distribution and temporal variability of UV radiation in Europe

The major geographical pattern in the UV radiation distribution is associated with latitude. Because the sun is higher on the horizon at lower latitudes, the radiation intensity increases from North to South. In July, the erythemal daily dose is typically 2 times higher in Southern Europe than in Nordic countries (see Fig. 2.4.1). This latitude pattern is present in all seasons but more pronounced as the daylight duration is shorter. This effect is stronger in the UV than in the visible spectral range.

Fig. 2.4.1: Average erythemal dose Fig. 2.4.2: Average erythemal dose in July over Europe. in April over the Alpine arc and a large part of Italy.

Fig. 2.4.2 shows a number of local effects. For instance, the enhancement of UV radiation over the Alps results from altitude, snow and low aerosol load. The thinner atmosphere and associated lower aerosol content reduce the backscattering of radiation to space. Snow reflects a substantial part of the incident radiation, a fraction of which is then backscattered from air molecules towards the surface. The lower Pô valley (north-eastern Italy, just below the Alps) exhibits lower doses with respect to areas at the same latitude in France and Croatia. This is caused by high average cloudiness and aerosol load.

UV radiation can be very variable from one year to the other. This variability is maximal in spring when the stratospheric ozone amount is itself very variable.

15 The other main factor is cloudiness, which can vary substantially from year to year. Fig. 2.4.3 shows a few examples: In the period 1958-2002, the cloudiness was particularly heavy over N-E Europe in March 1967, leading to low UV in this area. The high values in the same area in March 1974 are mostly attributable to low ozone. High UV over France and in the North in April 1997 results from the combination of low ozone and low cloudiness. Because the stratospheric ozone is more regular, the variability in summer is less pronounced (within ±30%) and is mostly caused by variable cloudiness.

Fig. 2.4.3: Variability of the monthly averaged erythemal daily dose in March 1967 and 1974, and in April 1997.

Fig. 2.4.4 illustrates the spatial variability of UV radiation spectrally weighted for its efficiency in the synthesis of pre-vitamin D 3 (see Fig.3.1). The action spectrum used is the one endorsed by the International Committee on Illumination (CIE 2006). The two images on the left represent the CIE 2006 weighted daily dose on March 10 th (top) and July 10 th 2000 (bottom) respectively. The influencing factors are the same as for the erythemal radiation: cloudiness, altitude, surface albedo, aerosols, solar zenith angle and total column ozone. However, the “vitamin D 3 efficient UV” is more sensitive to absorption by ozone than the erythemal radiation. With respect to the erythemal action spectrum, the CIE 2006 action spectrum indeed puts a larger relative weight on shorter wavelengths and is close to zero in the UV-A. As a consequence, the “vitamin D 3 efficient UV” decreases with high solar zenith angle more rapidly than the erythemal UV, as the effective path of the photons through ozone gets longer. This shows in the centre images of the panel

16 representing the ratio of CIE 2006 weighted to erythemal daily doses on the two days. In July and at low latitude, this ratio is close to two while it drops below one in the North in March. Obviously this ratio also decreases with the amount of total column ozone itself. One can see that the patterns in the ratio images correspond to the patterns of total column ozone on the corresponding days (images on the right).

th Fig. 2.4.4: March 10 (top) and July10th 2000 (bottom), vitamin D 3 CIE2006 weighted daily dose (left), ratio of vitamin D 3 CIE2006 weighted to erythemal daily dose (centre) and total column ozone field (right).

Surface UV radiation exhibits variations in different time scales ranging from minutes to decades. Such variability reflects many complicated processes affecting UV transmission through the atmosphere. The most pronounced periodical signals in the UV data are the daily and yearly courses related to sun elevation. In multi-scale analysis of the data it is convenient to use monthly fractional deviations, i.e., deviations of actual monthly means from the long-term monthly means expressed in percent. In this way, the strong yearly course is subtracted from the data. For many European sites the reconstructed UV series

17 are longer than 50 years. The analysis for Budapest shows that present UV level is 5-10% larger than before the 1980s. Such behaviour is found for many sites.

BUDAPEST BUDAPEST 4000 (%) 1950-2004 30 ERYTHEMAL UV DOSE 30 3500 25 25 20 20 )

2 3000 15 15

2500 10 10 5 5 2000 0 0 -5 -5 1500 -10 -10 -15 -15 Monthly Mean Dose Monthly(J/m Dose Mean 1000 Monthly Fractional Deviations Deviations Fractional(%) Monthly -20 -20 500 -25 -25 -30 2002: 11.3% (7.4%; 16.2%) -30 0 1950 1954 1958 1962 1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Fig. 2.4.5: Monthly mean daily erythemally weighted doses for Budapest since January 1950 (left panel), smooth curve fitted to monthly fractional deviations with 95% uncertainty range for May – September (right panel), illustrates UV trend and its uncertainty.

Long-term deviations of monthly mean erythemally weighted UV doses over Europe in 2002 relative to the base line level (1958-1978) are shown in Fig. 2.4.6. Positive (negative) departure means increasing (decreasing) UV level in the period 1979-2002. The UV increases over continental Europe, western part of North Africa and Svalbard are disclosed in the cold season. The UV increase over the continental Europe approaches 10% in the warm season and is slightly lower than that in the cold season. The statistically significant UV increases are found only over some isolated areas in the continental Europe during the warm season.

18 80 80 0 4 -2 10 8 2 10 6 4 75 -8 75 -6 -10

4 - - 6 4 70 70 2 6 -4 8 -6 8 -2 65 0 0 65 6 2 0

0 60 4 60 2 -2 0 0 4 2 55 8 55 6 8 1 80 12 10 50 14 50 4 0 4 8 1 0 2 45 1 1 1 45 14 2 4 6 2 40 40 4 6 8 8 4 2 4 0 35 8 1 0 35 30 30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35

- -4 -6 80 8 -10 6 80 -10 -4 - 0 -2 -8 0 75 0 75 -2 -2 4 - 6 - 70 0 2 70 -4 - -2 -2 0 65 4 65 2

6 4 2 60 8 4 60 2 4 0 55 2 55

-4 8 6 6

4 6 50 -4 50 2 6 4

- -2 10 1 -8 0 45 45 0 2 0 6 6 1 -2 0 0 1 40 0 4 -2 40 8 2 -2 35 0 35 4 2 4 2 30 30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14

Fig. 2.4.6: Departure of erythemally weighted UV radiation in 2002 relative to the base-line (1958–1978) UV level expressed in percent of the base-line value: cold season, October-April (top, left), warm season May-September (bottom, left). Dashed areas on the right panels represent regions with statistically significant departures.

Table 2.4.1 shows the UV departures in 2002 relative to the 1958-1978 base- line value over 5 0 latitudinal bands. Generally, the departures of UV level in 2002 are not dramatic compared with the past UV levels over Europe. The positive values are mostly found in the European mid-latitudes in October-April and for the whole year. For higher latitudes in May-September the UV departure is not statistically significant. It is worth mentioning occurrence of statistically significant negative departure in the warm season for the 75°–80°N band.

19 Band Warm Cold Year

35°– 40°N 2.1 (-0.3, 4.9) 6.3*(2.8, 9.5) 4.7*(2.2, 7.5)

45°– 50°N 0.8 (-2.3, 3.8) 6.5*(3.5, 9.6) 4.5*(1.5, 7.1)

55°– 60°N 1.8 (-1.7, 6.1) 1.3 (-2.0, 4.6) 1.2 (-1.2, 4.3)

65°– 70°N -1.2 (-4.0, 1.6) -0.7 (-4.6, 4.6) -1.4 (-4.4, 2.2)

75°– 80°N -4.8*(-7.8,-1.3) 1.9 (-4.1, 9.2) -2.4 (-6.2, 2.0)

Table 2.4.1: Departure of erythemally weighted UV radiation in 2002 relative to the long-term mean (1958-1978) in percent for warm season (May–September), cold season (October–April) and the whole year (January–December). 95% confidence ranges of the estimates are in the parentheses. Asterisks mark statistically significant results.

20 3. Biologically effective radiation

Solar radiation reaching the Earths surface causes a variety of different effects in livings. The effectiveness of solar radiation in causing an effect is not always the same. The effectiveness changes with the spectral intensity distribution of radiation. It changes with location, date, time and atmospheric conditions and the surrounding. Additionally the duration of exposure is essentially for an effect to become established or not. The relation between dose and response to UV radiation can be described by a dose-response curve (Fig. 3.1) whereas dose denotes the product of intensity and duration of irradiation. Dose-response curves are rarely simple straight lines. For some effects no response at low doses (offset) was found (as well known for the erythema) while others do react. Some effects develop first slowly (shoulder). Over a wide range the relation between dose and response is linear; the higher the dose the larger the effect. For many effects it was observed that at high doses the response increases less and less until there is no further increase although dose still does. To make it even more complicated the dose-response curve for a certain effect may change with wavelength.

ng 100 Taili 90 80 e 70 g n a 60 R

r a 50 e n i 40 L 30 Response[a.u.] 20 er Dose-Response ld 10 ou Sh 0

0 1 2 3 4 5 6 7 8 Offset Dose Dose [a.u.]

Fig. 3.1: Schematics of a dose response curve showing offset, linear range and tailing.

21 To estimate the effectiveness of UV radiation in causing a certain effect the action spectrum (or biological weighting function) has to be known to weight spectral irradiance. Action spectra are specific for each process and may differ obviously as DNA damage and photorepair (see Fig. 3.2) depending on the absorbing molecules. Frequently applied action spectra are shown in Fig. 3.3: human erythema and photosynthesis of vitamin D 3.

100 DNA-Damage 1 Photorepair Erythema (CIE 1987) 10 0.1 Vitamin D (CIE 2006)

1 0.01

0.1 1E-3 0.01 Effectiveness [1] Effectiveness Effectiveness [1] 1E-4 1E-3

1E-4 1E-5 280 300 320 340 360 380 400 420 280 300 320 340 360 380 400 Wavelength [nm] Wavelength [nm]

Fig. 3.2: Action spectra for DNA- Fig. 3.3: Action spectra for human Damage and photorepair. erythema and photosynthesis of vitamin D 3.

Collection and preparation of the action spectra for modelling was one of the tasks of COST Action 726 in order to allow future users of the reconstructed UV data of the past 50 years to choose the proper function for their specific interest. Examples of well documented action spectra can be found on the web-page: www.cost726.org . The following chapters give short summaries of the influence of UV on livings. Periodically reports about UV and life are elaborated by the United Nations Environmental Program (see Appendix C).

3.1. Biological effects of UV radiation on human body

The skin Solar radiation which is reaching the Earths surface interacts with human skin. It can be partly reflected, partly scattered and the rest penetrates into skin tissue. The depth of penetration depends on the wavelength. The UV-B radiation

22 penetrates only into epidermis, while UV-A into epidermis and dermis (dermis is the second skin layer situated under epidermis). Visible and infrared wavelengths penetrate even deeper into the skin. Only absorbed radiation is biologically active. The targets of this absorption are not only skin cells but any other e. g. immunocompetent cells. The immediate response after the UV exposition can be inflammation of the skin (erythema known as sunburn, even blisters) and suppression of immune reactions in the skin. One of term effects of UV can be the degradation of the folic acid content - a basic necessity for fertility. Long term harmful effects of UV radiation can be photoaging of the skin and skin cancer. UV-B rays act directly on skin tissue but UV-A also by reactive oxygen species creation (this is an issue for antioxidative therapy). Adverse reactions after UV exposition could be enforced by phototoxic action of some systemic (tetracyclines, thiazides, amiodarone, chlorpromazine, etc.) drugs or topically applied cosmetics, perfumes, chemicals (coal tar, bergamot oil, musk ambrette, etc.) Photoallergy can start also after contact with some sunscreens with chemical filters. Pathological sensitivity to solar radiation can persist as a real photodermatosis. On the other hand, the exposition to solar radiation contributes to positive psychogenic feeling. Seasonal affective disorder represents depression during winter after a lack of sunlight exposition. UV-B is also required for photosynthesis of vitamin D 3 in the skin. The vitamin D 3 is essential for calcium metabolism respectively skeletal health and plays a key role in postmenopausal osteoporosis. The “vitamin D 3 effective UV” can be calculated using the action spectrum for photosynthesis of vitamin D 3 (Fig. 3.3). Fig. 2.4.4 illustrates UV radiation spectrally weighted for its efficiency in the synthesis of vitamin D 3 over

Europe, for March and July (left panels). The vitamin D 3 effective UV decreases rapidly with high solar zenith angle (northern Europe). In regions and cases where the natural skin exposure to UV radiation is not sufficient to get enough

“vitamin D 3 effective UV”, the oral supplementation and vitamin D rich diet should be applied. Whole life consecutive solar radiation exposition may lead to a complex of microscopic or clinically apparent patterns called photoaging (Fig. 3.1.1 left panel). This is not only chronological aging with atrophy but other changes are

23 involved: freckles or hypopigmented spots, dry skin with keratotic lesions, “leather” skin with wrinkles, yellowish elastotic degeneration, cystic comedons and even skin tumors, including actinic keratoses, basal and squamous cell carcinomas (Fig. 3.1.1 right panel), melanoma. More than 90% of all skin cancers occur on sun-exposed skin. The face, neck, ears, forearms, and back of hands are the most common places it appears.

Fig. 3.1.1: Left panel: Photoaging of the skin with elastoidosis, komedons (blackheads) and keratoses. Right panel: Actinic keratosis of upper lip and basal cell carcinoma of nose

Skin type and natural photoprotection

The skin reaction after sun exposition differs in people. There are some dispositions: fair Caucasian skin burns very easily, dark skin of Negroes is protected by pigment melanin and usually never burns. We can divide all population into 6 skin types:

I Always burns easily; never tans II Always burns easily; tans minimally and with difficulty III Burns moderately; tans gradually, uniformly (light brown) IV Burns minimally; always tans well (moderate brown) V Rarely burns, tans profusely (dark brown) VI Never burns; deeply pigmented (black), tans profusely

People with skin types I, II are at greatest risk in the sun. The natural skin photoprotection involves some components including horny layer thickening and melanin pigmentation. The highest importance of epidermal thickness would be

24 expressed in type I. Suntan usually consists of 2 steps. Immediate pigment darkening which starts soon after sun exposure in darker pigmented individuals (provoked by UV-A), it is unstable reaction and disappears in a few hours. Permanent pigmentation reaction (provoked predominantly by UV-B) is clinically apparent in 2-3 days and lasts for 2-3 months.

Skin photoprotection

Shadow and clothing

The shadow affords a natural and effective photoprotection (hat, parasol, trees, etc.). Textiles photoprotection depends on yarn density and thickness. To a certain extend color may play a role as darker absorbs more light (but could overheat). Wet garments protect less. Artificial materials (nylon, dacron, etc.) are less transparent for UV radiation than cotton. The compression is an important factor in stretch garments. Some textiles are labeled by UV Protecting Factor (UPF), UPF over 50 signs high protection.

Sunscreens

Sunscreens are substances applied directly on the skin (solutions, gels, creams, lipsticks, etc.) with photoprotection ability (absorb or scatter UV radiation). The best sites for their application are the most exposed areas - nose, ears, lips. The sunscreens capacity is defined by Sun Protecting Factor (SPF). The higher SPF – the more efficient photoprotection affords (SPF multiplies the "safe" time of sunshine exposition). Photoprotection properties depend on its active part – filter (Fig. 3.1.2). Organic (chemical, absorbers) and inorganic (physical, mineral pigments) substances or natural oils (chemically not exactly defined) are distinguished. Topical sunscreens with high or very high SPF introduce usually mixtures containing both organic and inorganic filters.

25

Fig. 3.1.2: Principles of sunscreens photoprotection

a) Organic (chemical) filters (with large molecule and structure) absorb energy in the UV region and this absorption leads to their internal conversion which may cause problems with photostability. Contact photoallergy could limit the use of some substances as filters but new safer ingredients are dermatologic tested (Mexoryl XL, SX; Tinosorb S, M).

b) Inorganic (mineral pigments) filters scatter and reflect incident UV and visible radiation depending how large the particles are. Titanium dioxide, Zinc oxide, Magnezium oxide, talcum are mineral substances without allergenic potency. Mineral filters in higher concentration are more difficult to spread on the skin and the white shade is cosmetically unpleasant.

c) Natural oils (originated from plants: aloe extracts, jojoba oil) have lower SPF. Their emollient and antioxidative properties are useful.

The topical sunscreens have to be carefully applied, according to instructions. The protection achieved is often less than that expected and depends upon a number of factors: application thickness and technique, type of sunscreen applied, resistance to water immersion and mechanical abrasion, and when, where and how often, sunscreen is re-applied. Information about actual UV-index or "safe" time on the sun (till redness apears) for each phototype is required for correct choice of SPF.

26 New trend in topical photoprotection is to enhance repair of UV damage in human skin (using DNA repair enzymes). Human skin as a radiation exposed tissue can be affected by photooxidative stress. Antioxidative defense (trapping free oxygen radicals) of the skin could be supported by ascorbate, tocopherols and carotenoids additives in sunscreens.

The eye Acute effect of UV exposure includes photokeratitis (welders flash, snowblindness) of the eye. Chronic UV irradiation leads to the conjunctiva hypertrophy (pterygium) and droplet keratopathy. The iris contents melanin that represents one of the natural protectors of the inner eye. Unfortunately melanoma rising from its tissue could be dependent on solar UV exposition. People with blue eyes are affected threetimes frequently compared to brown eyes people. Lens is made from regular peptide fibres important for its transparency. Chronic UV exposure leads to desintegration architecture of lenses and loss of transparency (cataract). Also depletion of anti-oxydative properties of lens enzymes according to age, represents a risk of blindness. The main reason of elderly blindness is macular degeneration of retina. This is a death of light-sensitive cells in the central part of retina caused by light exposition, decrease of antioxidative substances and failure of tissue supplementation.

Eye photoprotection

The eyes can be protected by sunglasses containing UV-B and UV-A filters. Because of the lateral exposure, it is recommended to wear wrap-around sunglasses. Also high energy visible radiation (400-500nm) could damage the retina and so photoprotection in this spectrum is requested as well. Only sunglasses with guaranteed protecting filters should be used.

3.2. UV Radiation and Animals

Much of information on the photobiological effects of UV radiation on humans results from animal studies respectively from mammals. Despite that, rather less is known about the influence of UV radiation on wild living animals. Since the

27 1920s the carcinogenicity of UV has been investigated, mostly in mice, rats, guinea pigs, and hamsters. Skin tumours have been reported also in domestic and food animals including cats, dogs, cows, sheep and goats. Sun burn is found in food animals especially when hold under in-appropriate environmental conditions. Affected are those parts of the body with spares fur. Most sensitive to UV radiation are animals with little fur, and/or reduced pigmentation whereas cultured races are on high risk.

Fig. 3.2.1: Sun burned piglet (kept free-range).

A large number of studies have reported acute and delayed ocular effects as photokeratitis, photoconjunctivitis or cataract in laboratory experiments and in free living animals. Immune response to UV radiation in animals is a sophisticated topic because it goes hand in hand with tumour development, susceptibility to immunologically- mediated diseases and infection diseases. Folic acid content - a basic necessity for fertility - can be degraded by UV radiation too. Mammals are not defenceless at the mercy to UV radiation. During evolution photoprotective and repair mechanisms were developed to ensure survival of species in their natural habitat. On the other hand, several kinds of animals when kept indoors, like monkeys in zoological gardens, birds or reptiles, may need UV supplement for health. In many species, vitamin D 3 production can only become initiated by UV radiation because they lack the ability to uptake vitamin D 3 from diet. Vitamin D 3

28 regulates, amongst others, the calcium metabolism. Insufficiency causes rickets and osteomalacia or reduces egg hardening. Interaction of UV and birds has a further component. Chicken, pigeons and others possess UV sensitive receptors in their eyes so that they can use UV radiation for visual orientation. Additionally UV radiation can stamp the circadian clock of birds. Some of the aquatic vertebrates are also visually sensitive to UV and make active use of it, like for depth control. Erythema and carcinogeneticy from UV were observed too. Beside the adults, eggs are affected by UV as enhanced UV increases mortality of embryos. Damage during egg stage may lead to deformation in adulthood as it was found in some species of amphibian. Recently it was observed that egg-wrapping behaviour protects new embryos also from UV radiation. For insects the interaction between UV and life is quite complex. Many species have visual receptors for UV radiation. They may use UV radiation for orientation and navigation. The fact that UV attracts insects is applied in hygiene applications, like pest control devices or fly traps. Reflection plays an important role in the visual world of insects. Reflection of UV from wings or other body parts are often used to identify mates. UV reflection patterns allow also the identification of plants as a food source or as place for reproduction. To make it even more complex, UV radiation regulates the anti pesticide capability of plants for defence on insects. Additionally, UV radiation may stamp the time of the circadian clock and may act as trigger in-between different stages of development. Development is often bounded to other environmental conditions (temperature, availability of food, ...) so that a shifted internal clock may be fatal. Through their high rate of reproduction and high selection pressure, insects but also other animals, have the ability to adapt to environmental changes to a certain extend. Recently it was found that the cosmopolitan common fruit fly (Drospohila) can even adapt genetically to climate changes at a time scale of 20 to 30 years. Animals possess also a disposition to migration. This may ensure survival but may have detrimental effects for the conquered region.

29 Molluscs are generally very sensitive to UV radiation. However, their environs and their behaviour ensure that the received UV radiation is minimal. In certain cases however, they have to move outside their safe environment. The degree of sensitivity and movement are adapted for this. A changed UV regime influences daytime and duration of being outside and the length of distances that can be moved. In the past, research on UV and animals was often animated by getting information for human health applications. After the discovery of the ozone hole and the global ozone depletion the effects of UV on animals were studied more frequently. Global climate change is nowadays a new ignition for research activities. Species preferably under study are still those which are of commercial relevance. The influence of a change in ambient UV radiation on animals depends on many circumstances. Animals, living mainly underground, will be affected rarely. Animals , active all day in a rather unshadowed environment may be affected seriously. The short life span of many animals limits the development of chronic damage and diseases. However, the effects from UV radiation may become serious because already a slight curtailing in vitality can be fatal e.g. in recognising and escaping predators. With these, mean life span can decrease denoting a shorter period for reproduction and for upbringing offspring. If already eggs of a species are sensitive to UV radiation, then the long-term adapted equilibrium between amount of eggs and the number of animals reaching adulthood will be disturbed. The world of animals will change as climate and the natural UV radiation environment change and it will change much more than the world of humans. At this time, nobody can foresee what may happen because of the extreme complexity of interactions.

3.3. Micro-organisms and UV radiation

Micro-organisms are everywhere. Micro-organisms can be found in the air, in waters, in the ground, on surfaces and inside other organisms. What we call micro-organisms or microbes consists of a variety of types of very small livings. They are so manifold and different as one can imagine. Micro-

30 organisms include viruses, bacteria, fungi and protozoa. Their size may be as small as the wavelength of light. For humans and animals a variety of microbes are necessary to stay healthy while other microbes can cause severe diseases. Micro-organisms can be damaged by UV radiation easily. Damage can be manifold like grow reduction, reduction of reproduction rate, of metabolism rate, of infectivity, of mobility and others. Hygiene applications like disinfection make use of UV inactivation. Inactivation means that micro-organisms lose the ability of reproduction. UV inactivation occurs as a result of the direct absorption of UV radiation by the micro-organism. This brings about an intracellular photochemical reaction that changes the biochemical structure of nucleic acids. These changes may lead to the inhibition of transcription and replication of nucleic acids, thus rendering the organism sterile and disables infection when entering a host. The wavelength range where UV is most effective in inactivation is quite similar to that where DNA has the highest absorbency (UV-C and UV-B range) with maximum effectiveness - of course outside the natural UV - around 265nm. The range of highest efficiency is also called germicidal range. Dose-response curves vary. For some micro-organisms no response at low doses was found while others do react. Some show a slow increase with dose. In the middle part response is mostly linear. For high doses the increase of response may become weak again. Micro-organisms which possess pigments in their outer layer are more resistant. High resistant to UV radiation are spores and (oo)cysts. However sensitivity varies quite high within a group, even by a factor of ten. Recently, studies have reported an increased UV resistance of environmental bacteria and bacterial spores, compared to lab-grown strains. This means that they could have the ability to adapt to their UV environment. Free moving micro-organisms receive UV radiation from all directions. With that the optical properties of the surrounding medium are important. Solid or organic particulate matter in water or air, reduces transmittance of UV. Micro-organisms have also the ability to adhere on surfaces so, they can make use of particulate matter as radiation protection and vehicles. Clumping of micro-organisms is also a strategy of radiation protection.

31 Additionally, effectiveness of UV is decreased by magnitudes if a (pathogenic/parasitic) micro-organism has entered a host. Micro-organisms – as all other livings - are not defenceless at the mercy to UV radiation. There are repair mechanisms that may equalise damage to a certain degree. Nucleid acids, for example, can be repaired in a process termed ‘photoreactivation’ in the presence of light, or ‘dark repair’ in the absence of light. Damage is not the only effect of UV radiation to micro-organisms. UV may also act in igniting new stages in development like sporulation in many species of fungi. Also a variety morphogenetics depend on UV. Micro-organisms can make use of UV for environmental information too. As any other livings, micro-organisms are adapted quite well to their environment. In generally, an increase of UV radiation is detrimental resulting in a reduced life span, a decreased ability of reproduction, a shorter pathway, a reduction of the habitat or a decreased number in the species. But, there are many ways where micro-organisms may profit from environmental or climatic changes. Decreased UV radiation e.g. by enhanced cloudiness, aerosol load or dust, result in a decreased damage which may allow a longer pathway to find a potential host. In the case of pathogens a higher transmission and outbreaks of diseases may occur more frequently. The seasonal outbreak pattern of influenza in many parts of the world is a prominent example. Differences in the outbreak between Spring and Autumn can be explained by different total ozone content and cloudiness, which change the relation between damage and photoreactivation. If other environmental parameters change (like temperature), micro-organisms can settle in a new environment where damage through solar radiation is maybe lower and potential hosts are not prepared to the blight. It was observed, that during the past years pathogens have already started migrate to northern latitudes.

32 3.4. UV radiation and Plants

The effect of UV radiation on vegetation is a relatively new field of scientific research. A strong rationale for such research has been the attempt to understand and quantify the possible effect on plants of the increase of UV-B irradiance at ground, associated with the depletion of the stratospheric ozone layer. Results of first pioneer researches were impressive, showing dramatic reductions in the photosynthesis and consequently in plant growth and crop yield. Nevertheless, it was later demonstrated that they were strongly affected by the fact that the experiments were conducted in growth chambers or glasshouses, which tended to exaggerate the negative effects of high UV-B on vegetation. The unrealistic low level of radiation at other wavelengths, active in the damage repair mechanisms, erroneously conditioned these experiments. During the 1990s new experimental approaches were developed to study the effect on vegetation of both, enhanced and attenuated UV in field conditions. The experiments on enhanced UV were conducted supplementing the global solar radiation with UV-B emitting fluorescent lamps. In the second case, the UV in global solar radiation was attenuated using spectrally selective plastic films. These new experiments indicated that the effects of UV radiation on plants were more modest, subtle and in many cases indirect. They further indicated that also UV-A component, whose role was underestimated for a long time, may have important effects and has to be taken into consideration.

Direct effects

UV-B can cause stresses or act as a developmental signal, depending on its fluence levels, but little is known about how non damaging low-fluence-rate UV- B is perceived to regulate plant morphogenesis and development. Large body of knowledge acquired in recent years, indicates two major consistent responses of vegetation to changes in UV irradiance at ground: a moderate reduction in the growth and a relevant modification of plant biochemistry. High levels of UV-B tend to depress plant growth, affecting plant biomass including root system. This is mainly due to a reduced leaf expansion, that is

33 more affected than photosynthesis efficiency per unit leaf area. Cell enlargement has been demonstrated to inversely respond to light quality and quantity: high level of UV (mainly UV-B) inhibits cell enlargement and leaf expansion resulting in a smaller leaf dimensions. Plant height is also negatively affected by UV levels as well as plant architecture which is also influenced by changes in the quantity and quality of solar radiation distribution (including UV components) along the canopy profile. These effects on plant growth characteristics were found to be species specific: consequently they can strongly affect competition between different species both in natural ecosystems and crops. Allocation of biomass is another growth factor affected by UV radiation. Under high UV the root/shoot ratios is significantly affected, mainly because of larger limitation to root biomass. Since UV penetration into the soil is marginal, this phenomenon is generally explained invoking a systemic response of the root system to the above ground UV irradiance. Nevertheless, more recently it has been hypothesized a direct perception of roots even at low UV-B fluence rates. Plant chemistry of secondary metabolites is the other main target of UV radiation. The accumulation of UV-absorbing pigments in the vacuole of the epidermal cells is the more efficient mechanism of plant acclimation to high UV radiative environments. The major chemical compounds involved are phenolic compounds, such as flavonoids: they act as selective filters attenuating UV transmission without modifying the visible region of the spectrum, primarily the Photosynthetic Active Radiation (PAR) (Fig. 3.4.1). It is worth to remember that some of these UV-filtering compounds have also an antioxidant function. Finally, UV radiation has influence also on the abundance of other substances that may be appreciated in the food production (in horticulture as well as in viticulture) or by the pharmaceutical industry, that could derive antioxidant products, essential oils or natural dyes from some species properly exposed to UV radiation.

34

Fig. 3.4.1: Adaxial epidermis (leaf) of enhanced UV-B (left) and normal solar radiation treated Oak plants (right). Accumulations of phenolic compounds (protection) are clearly visible in the secondary wall of cells in UV-B treated leaf.

Indirect effects

UV radiation has also a relevant ecological role, influencing the interaction of plants with animals and other micro-organisms. UV radiation stimulates expression of genes that play a primary role in the plant defence from several biotic and a-biotic stressors and in particular from pathogens attack, suggesting an important role of UV radiation in promoting resistance to plant diseases. In fact two different responses to UV radiation are active during a pathogen attack, one being directly related to a reduced pathogen aggressiveness (in particular for “naked” pathogens) and the other connected to an increased host resistance to the attack stimulated by the accumulation of UV-induced substances. UV radiation and plant-animal interaction : The accumulation in the tissues of plants exposed to high UV radiation of secondary metabolites (phenolics) and carbohydrates and nitrogen compounds, tends to reduce the attractiveness for herbivore insects and in some cases also for oviposition. Moreover, changes in the secondary metabolism induced by UV, may be responsible for improvement in the forage quality for ruminants thanks to improved digestible dry matter content. Nevertheless, this effect is species specific and dependent on other environmental parameters as rainfall. Decomposition of leaf litter is also affected by UV-B radiation as a result of both, photochemical breakdown of complex

35 compounds (lignin) and modification of the decomposer population active in the soil. The latter may be associated to changes in the root exudates composition and quantity stimulated by changes in the above ground UV irradiation. Interaction with other environmental parameters: Actual understanding of the interaction of UV radiation with other environmental parameters, like CO 2 concentration, temperature, soil water availability and soil nutrient content, is yet limited and further investigations are needed mainly for possible impact of climate changes on terrestrial ecosystems.

3.5. UV and aquatic systems

Transmittance of UV radiation

UV radiation penetrates water and even ice and snow. A modest snow cover of 15cm reduces UV levels to the ground by approximately two orders of magnitudes. In ice a reduction of UV in the orders of two magnitudes is caused by a layer of 2.5 m. Transparency depends on age and clearness of the ice and on wavelength. The UV-B is attenuated stronger than the UV-A and the visible radiation. Penetration of water depends as well on wavelength and on the optical properties of water, however transmittance in water is much lower than in the atmosphere. At the water-air boundary the index of refraction changes and must be taken into account. Reflection of UV at the boundary is in the order of 10%. Transmittance through water depends on the clearness. The depth for a 10% transmission can vary from about dozens of meters to a few centimetres in brown humic waters. Solvents as salinity decrease transmittance, but most important is the amount of absorbing and scattering particles in the water. Especially in eutrophic fresh water systems and coastal regions the transparency is affected strongly by these particles. Main contributors are the so-called “yellow substances”, chlorophyll and other photosynthetic pigments, as well as dissolved particulate organic and inorganic matter. UV is also absorbed and scattered by organisms living in water as plantkton, algae and sea grasses that may build large canopies.

36 Transparency of water is not constant over time but shows a temporal (seasonal) variability which goes hand in hand with the changing amount of solved and dissolved matter in the water. Meteorological factors may cause also variability – snow melting and flood water may transport large amounts of unsolved substances. In general, transparency is highest in the clear ocean water and high alpine lakes and lowest in brown (humic) waters. UV radiation on sessile aquatic livings becomes extreme in regions were water lacks from time to time as caused by low water flow and by tides. As it can be seen from Fig. 3.5.1 and 3.5.2 shorter wavelength UV radiation is absorbed more than longer wavelength UV. Fig. 3.5.2 shows modelled values for DNA-damage weighted spectral solar irradiance for different depth levels in ocean and coastal water. It can be seen that the ozone affected UV-B range delivers the highest amount of irradiance for DNA-damage, although UV-B from the sun and transmittance through water are lower than for UV-A.

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Effects on aquatic livings

As in other ecosystems most of the photoeffects on aquatic livings are driven by the visible solar radiation but a considerable fraction is due to the UV wavelengths. The largest part of the earths biomass results from bacterioplankton and picoplankton, phytoplankton, zooplankton, cynobacteria, macroalgae and seagrasses. Compared to these, the biomass of higher organisms is negligible.

37 Plankton

Bacterioplankton, nanoplakton and picoplankton decompose organic matter in water and play an important role in the carbon flux of the ecosystem. Bacterioplankton may serve as food for picoplankton and as host for viruses. These types of plankton do not possess protective UV screening pigments and are therefore high sensitive to UV radiation. Main target of UV is DNA. Protection is mainly through photoreactivation. Vertical mixing of water brings them also somewhat deeper where damaging UV-B is lower and photoreactivating UV-A and blue light is relatively higher.

Phytoplankton is the most important biomass producer in aquatic ecosystems. Phytoplankton can be found in the top layer of waters where they receive enough photosynthetic radiation. This layer can range from a few decimetres to hundred metres in clear water. UV effects photosynthesis, metabolism, growth, reproduction, survival and distribution. Phytoplankton may actively swim or use buoyancy to reach the optimum depth. However, wind and waves can disturb their vertical distribution. Phytoplankton is feed for zooplankton and higher organisms. Radiation protection is provided by caretenoids and pigments. As some of the latter are chemically quite stable, they can be found in the sediments of lakes and therefore, it could be possible to reconstruct UV into the past.

Main target for UV in zooplankton is DNA and effects are similar to other small livings. Their protection against UV results from depth control in the water and from pigmentation. However, depth depends also on the availability of food sources (plankton).

Algae and seagrasses

Blue-green-algae (Cynobacteria) possess a plant-type oxygenic photosynthesis. Several kinds of cynobacteria are able to fix atmospheric nitrogen. They have a high degree of adoption to different environmental conditions and being therefore cosmopolitans. Cynobacteria can be found also in wet soil like in rice paddies and are therefore involved in one of the human most important food production. UV radiation effects not only survival but also

38 motility, growth, photosynthesis, metabolism. Pigmentation of cynobacteria is a well working sun protection for their DNA. UV exposure of macroalga and seagrasses varies very much. Some kinds grow at coast and are even above the water during tidal changes, other live always under water up to depth, were light is some orders of magnitude less intensive than at the surface. As higher plants, macroalgae use the same photoinhibition mechanism for protection from high irradiance. Effects of UV on seagrasses are similar to that on ground plants. They play an important role as habitats for higher organisms.

39 4. Expectations for the future

The levels of surface UV radiation in the future will depend on the variations of radiation emitted by the Sun and on the evolution of various factors, known to influence the propagation of solar UV radiation through the atmosphere. These factors include ozone, aerosols, clouds, UV absorbing air pollutants and surface reflectivity, and are strongly linked with Climate Change. A comprehensive discussion on the likely future changes of UV irradiance at the Earths surface is included in the most recent Scientific Assessment of Ozone Depletion: 2006 (WMO, 2007) and the Environmental Effects of Ozone Depletion and its Interactions with Climate Change: 2006 Assessment (UNEP, 2006). For the next few centuries, the expected changes of solar output due to orbital variations of the Earth, the so called Milankovich cycles with periods between 40000 and 20000 years, are very small (less than 1%). Similarly sub-percent changes in UV-B and UV-A radiation are expected from the changes in solar activity (i.e. the sunspot number variations with periods of 11 years and their 27-days rotation). Thus, mainly the changes in the earth’s atmosphere will dominate the variations of surface UV radiation in the coming centuries. Stratospheric ozone is one of the major factors which determine the levels of surface UV radiation. During the last third of the 20 th century stratospheric ozone has been severely depleted and its concentrations continue to be low, particularly in Antarctica. Recent observations suggest that the concentration of ozone depleting substances in the atmosphere have started to decrease as a result of the measures taken under the Montreal Protocol and its Amendments and Adjustments (WMO, 2007), marking the onset of the stratospheric ozone recovery (Yang et al., 2008; Angell and Free, 2009). As ozone will be returning to its pre-1980 levels, surface UV radiation will be decreasing accordingly. Climate change will influence cloudiness, aerosols and surface albedo in a complex manner introducing regionally and seasonally different effects (IPCC, 2007). Consequently, surface UV radiation changes due to these factors are also expected to vary between regions and seasons. Yet, the links between climate change and ozone depletion are not clearly understood increasing the uncertainty about the timing of the ozone recovery (e.g., Waugh et al., 2009).

40 Coupled Climate Chemistry models provide future predictions of the above mentioned UV influencing factors allowing the simulation of surface UV levels in the coming decades (WMO, 2007; Eyring et al. , 2007; Tourpali et al. , 2009). Under cloud free conditions, surface erythemal irradiance has been calculated to decrease globally as a result of the projected stratospheric ozone recovery at rates that are larger in the first half of the 21 st century and smaller towards its end. Between 2000 and 2100 the decrease over midlatitudes ranges between 5 and 15%, while at the southern high latitudes the decrease is twice as much. Since effects from changes in cloudiness, surface reflectivity and tropospheric aerosol loading, have not been considered, over some areas the actual changes in future UV radiation may be different depending on the evolution of these parameters. According to the Fourth Assessment Report of the IPCC 2007, multi-model simulations based on the SRESA1B scenario suggest that cloud cover will decrease by the end of the 21 st century in most of the low and middle latitudes of both hemispheres by up to 4%. This would result in an increase in surface UV radiation in these regions (e.g. by about 4% for erythemal irradiance), counteracting the decrease from ozone recovery. The opposite is expected in high latitudes and in a few low-latitude regions where cloud cover is predicted to increase. A decrease in surface reflectivity in the high to polar latitudes of both hemispheres due to reduction of ice covered areas (e.g., Overland and Wang, 2007; Comiso et al., 2008) would result in a decrease of surface UV radiation over these and neighbouring areas, enhancing the projected decrease in surface erythemal irradiance due to changes in ozone. Surface reflectivity enhances the upwelling radiation, part of which is backscattered by atmosphere thus increasing the irradiance at the surface and over areas within several kilometres. In summary, the projected recovery of the ozone layer during the 21 st century in conjunction with the expected changes in other UV influencing factors due to climate changes are expected to modify accordingly the UV solar irradiance at the Earth’s surface. In general, decreases are largest in areas where the ozone depletion has been most pronounced, such as over Antarctica. The projected UV changes have large uncertainties due to the approximations inherent in the assumptions for cloudiness, aerosols and surface albedo.

41

Fig. 4.1: Adapted from (WMO, 2007), Executive Summary. (a) Production of ozone-depleting substances (ODSs) before and after the 1987 Montreal Protocol and its Amendments, from baseline scenario A1. Chlorofluorocarbons (CFCs) are shown in black: additional ODSs from hydrochlorofluorocarbons (HCFCs) are in gray. Note: HCFCs, which have been used as CFC replacements under the Protocol, lead to less ozone destruction than CFCs. (b) Combined effective abundances of ozone-depleting chlorine and bromine in the stratosphere. The range reflects uncertainties due to the lag time between emission at the surface and the stratosphere, as well as different hypothetical ODS emission scenarios. (c) Total global ozone change (outside of the polar regions: 60 oS- 60 oN). Seasonal, quasi-biennial oscillation (QBO), volcanic, and solar effects have been removed. The black line shows measurements. The gray region broadly represents the evolution of ozone predicted by models that encompass the range of future potential climate conditions. Pre-1980 values, to the left of the vertical dashed line, are often used as a benchmark for ozone UV recovery. (d) Estimated change in UV erythemal (“sunburning”) irradiance for high sun. The gray area shows the calculated response to the ozone changes shown in (c). The hatched area shows rough estimates of what might occur due to climate-related changes in clouds and atmospheric fine particles (aerosols).

42 Appendix A: Reference Institutions in the COST726 Countries

Austria Czech Republic 1. Institute of Medical Physics 1. Solar and Ozone Observatory and Biostatistics, University of of the Czech Veterinary Medicine, Hydrometeorological Institute, Veterinaerplatz 1, Hvezdarna 456, 500 08 A-1210 Vienna Hradec Kralove 8 Mr. Alois W. Schmalwieser , Mr. Michal Janouch , Tel: +43 1 250774324 Tel: + 42 0 495260352 2. Institute of Meteorology, 2. Department of Dermatology, University of Natural Medical Faculty Hradec Resources and Applied Life Kralove, Charles University Sciences, Peter Jordan Prague, Sokolska 581, 500 05 Strasse 82, A-1190 Vienna Hradec Kralove Mr. Philipp Weihs , Mr. Karel Ettler , Tel: + 43 1 470582822 Tel: + 42 0 495836357

Belgium Denmark 1. Royal Meteorological Institute 1. Danish Meteorological of Belgium (R.M.I.B.), Institute, Lyngbyvej 100, 2100 Ringlaan 3, B-1180 Ukkel Copenhagen Mr. Hugo de Backer , Mr. Paul Eriksen , Tel: + 32 2 37305 94 Tel: + 45 39157500

Cyprus Estonia 1. Cyprus Meteorological Service, 1. Tartu Observatory, 61602, Nikis 28, CY- 1418 NICOSIA Tõravere, Tartumaa Mr. Marios Theophilou , Mr. Kalju Eerme , Tel: + 35 7 22332878 Tel: +37 2 7410 258 Ms. Sophia Louca ,

Tel: + 35 7 22802926

43 2. Deutscher Wetterdienst, Finland Meteorologisches 1. Finnish Meteorological Observatorium – Richard- Institute, Meteorological Aßmann-Observatorium, Am Research Division, Ozone and Observatorium 12, 15848 UV-radiation Research Group, Lindenberg POB 503 (Vuorikatu 19), FIN- Mr. Uwe Feister , 00101 Helsinki Tel: + 49 33 67760143 Mr. Jussi Kaurola , 3. Universität Hannover, Institut Tel. + 358 9 19294181 für Meteorologie und Mr. Anders Lindfors , Klimatologie, Herrenhauser Tel: + 358 9 19294170 Str. 2, D-30419 Hannover Mr. Gunther Seckmeyer , Tel: +49 51 17624022 France

1. Laboratoire d'Optique

Atmosphérique, Université des Greece Sciences et Technologies de 1. Aristotle University of Lille, 59655 Villeneuve d'Ascq Thessaloniki, Physics Ms. Colette Brogniez , Department, Laboratory of Tel: + 33 3 20436643 Atmospheric Physics, Campus 2. Météo-France, 42 avenue G. Box 149, 54124 – Thessaloniki Coriolis, F-31057 Toulouse Mr. Alkiviadis Bais , Cedex 1 Tel: + 30 2310 998184 Ms. Aline Peuch , 2. University of Patras, Physics Tel: + 33/0 5 61078084 Department, Laboratory of

Atmospheric Physics, 26500 –

Germany Patras Mr. Andreas Kazantzidis , 1. Ludwig-Maximilians Universität Tel: + 30 2610 997549 Meteorological Institute,

Department of Physics,

Theresienstr. 37, 80333

Muenchen

Mr. Peter Koepke ,

Tel: +49 89 21804367

44 2. Laboratory of Radiation Hungary Research National Institute of 1. Hungarian Meteorological Public Health and the Service, Measurement Environment (RIVM), P.O. Box Techniques and Methodology 1, 3720 BA Bilthoven Division, Gilice tér 39, H-1181 Mr. Harry Slaper , Budapest Tel: + 31 30 2743488 Mr. Zoltan Toth , Tel: + 36 1 3464857 Norway Mr. Zoltan Nagy , 1. Norwegian Radiation Tel: + 36 1 3464857 Protection Authority (NRPA), P.O.Box 55, N-1332 Italy Oesteraas 1. C.N.R. IBIMET, Via Caproni 8, Mr. Bjorn Johansen , 50144 Firenze Tel: + 47 67 162549 Mr. Gaetano Zipoli , 2. Norwegian University of Tel: + 39 055 3033711 Science and Technology 2. Univesità di Roma 'La (NTNU), Department of Sapienza', Physics Physics, N-7491 Trondheim Department, P.le A. Moro 2, Ms. Berit Kjeldstat , 00185 Rome Tel: + 47 73 591995 Ms. Anna Maria Siani ,

Tel: + 39 064 9913479

Poland 1. Centre of Aerology, Institute of Netherlands Meteorology and Water 1. Royal Netherlands Management, Zegrzynska 38, Meteorological Institute 05-119 Legionowo (KNMI), P.O. Box 201, 3730 Ms. Zenobia Litynska , AE De Bilt Tel: + 48 22 7673100 Mr. Michiel van Weele,

Tel: + 31 30 2206410

45 2. Satellite Research Department, Institute of Slovakia Meteorology and Water 1. Slovak Hydrometeorological Management, Piotra Borowego Institute, Poprad-Ganovce 14, 40-045 Krakow 178, 05 801 Poprad-Ganowce Ms. Bozena Lapeta , Mr. Miroslav Chmelik , Tel: + 48 12 6398194 Tel: + 421 527731097 3. Institute of Geophysics, Polish 2. Slovak Academy of Sciences, Academy of Sciences, Ksiecia Geophysical Institute, Janusza 64, 01-452 Warsaw Dubravska cesta 9, 845 28 Mr. Janusz Krzyscin , Bratislava Tel: + 48 22 6915874 Ms. Anna Pribullova , Tel: + 420 527879146

Portugal 1. Instituto de Meteorologia de Spain Portugal, Delega¹Ño Regional 1. Instituto Nacional de Técnica dos Azores, Observatorio Aeroespacial – INTA, Ctra. Afonso Chaves Rua MÑe de San Juan del Puerto- Deus – RelvÑo, 9500-321 Matalascañas Km 33, SP- Ponta Delgada, Azores 21130 Mazagón, Huelva Ms. Fernanda do Rosario da Mr. Jose Manuel Vilaplana Silva Carvalho , Guerrero , Tel: +351 296650210 Tel: + 34 959 208858 2. Instituto Nacional de Meteorología, Izaña Romania Atmospheric Observatory, C/ 1. National Institute Meteorology, La Marina 20, 6º Planta, SP- Hydrology and Water 38071 Santa Cruz de Tenerife, Administration PO-BOX 880 Mr. Constantin Rada , Mr. Alberto Redondas Marrero , Tel: + 40 21 2303116 Tel: + 34 922 373878 Ms. Laura Manea , Tel: + 40 21 2303116

46 Sweden EC JRC 1. Swedish Radiation Safety 1. European Commission, Joint Authority (SSM), Solna Research Centre, Institute for strandvag 96 SE-17116 Environment and Stockholm Sustainability, via Enrico Fermi Mr. Ulf Wester , 2749, 21020 Ispra (VA) Tel: + 46 8 7297171 Mr. Jean Verdebout , 2. Swedish Meteorological and Tel: + 39 0332 785034 Hydrological Institute, SE-601 76 Norrköping Mr. Weine Josefsson , WMO Tel: + 46 11 4958000 1. World Radiation Data Centre (WRDC), Voeikov Main Geophysical Observatory, Switzerland Karbyshev Str. 7, 194021, St. 1. MeteoSwiss, C.P 316, CH- Petersburg 1530 Payerne Mr. Anatoly Tsvetkov , Mr. Laurent Vuilleumier , Tel: + 812 2474390 Tel: + 41 26 6626306 2. Physikalisch- Meteorologischews Russia – non-COST Observatorium Davos/World country Radiation Center 1. Geographical Faculty, Moscow (PMOD/WRC), Dorfstrasse 33, State University, GSP-1, CH-7260 Davos Dorf Leninskie Gory, Moscow, Mr. Julian Gröbner , 119991 Tel: + 41 81 4175157 Ms. Natalia Chubarova , Tel: + 7495 9392337

United Kingdom 1. University of Manchester, SEAES, Sackville Street Building, P.O.Box 88, Manchester M60 1QD Ms. Ann R. Webb , Tel: + 44 (0) 1613063917

47 Appendix B: List of www pages with UV information

Austria Estonia http://www.uv-index.at http://sputnik.aai.ee/koduleht http://www-med-physik.vu- wien.ac.at/uv/uv_online.htm Finland www.fmi.fi/uvi Belgium http://www.meteo.be/meteo/view/en/522 044-UV.html France http://www.meteo.be/meteo/view/en/652 http://www.soleil.info/uv-meteo/ 39-Home.html http://ozone.meteo.be/meteo/view/en/13 Germany 51412- http://www.uv-index.de OzoneC+UV+and+Aerosol+studies.html http://orias.dwd.de/promote/index.jsp http://www.aeronomie.be/en/topics/inter http://www.suvmonet.de planetary/uv_live_belgium.htm http://www.dwd.de/mol/

Cyprus Greece http://lap.physics.auth.gr/uvnet.gr www.uvnet.gr

Czech Republic Italy http://www.chmi.cz/meteo/ozon/UV_onli http://www.uv-index.vda.it ne.html

Netherlands Denmark http://www.temis.nl/uvradiation/index.ht http://www.dmi.dk/dmi/index/danmark/s ml olvarsel.htm http://www.knmi.nl/kodac/weer_en_gez http://www.dmi.dk/dmi/index/verden/uv_ ondheid/zonkracht.html idag.htm http://www.rivm.nl/milieuportaal/onderw http://promote.dmi.dk erpen/straling-en-EM- velden/ultraviolette-straling/

48 Norway Switzerland http://www.nrpa.no/uvnett/default_en.as http://www.uv-index.ch/de/home.php px http://www.meteoswiss.admin.ch/web/e http://retro.met.no/varsel/index.html n/weather/health/uv-index.html http://uv.nilu.no/index.cfm?fa=uv.main http://www.meteoswiss.admin.ch/web/e http://www.fys.uio.no/plasma/ozone/ n/weather/health/uv- index/uv_measurement.html http://www.meteoswiss.admin.ch/web/e Poland n/weather/health/uv- http://www.pogodynka.pl/polskauv.php index/uv_radiation.html http://www.igf.edu.pl/pl/zaklady_naukow http://www.meteoswiss.admin.ch/web/e e/fizyki_atmosfery/ozon_uv n/research/projects/cost_726.html

Portugal United Kingdom http://www.meteo.pt/en/ambiente/uv http://www.hpa.org.uk/webw/HPAweb& HPAwebStandard/HPAweb_C/1195733 761671?p=1158934607746 Slovakia http://www.shmu.sk/sk/?page=73 Intersun, World Health Organization (WHO) Spain http://www.who.int/uv/en/ http://www.aemet.es/es/eltiempo/observ acion/radiacionuv

Sweden http://www.smhi.se/cmp/jsp/polopoly.jsp ?d=7850&l=en http://produkter.smhi.se/strang/ http://produkter.smhi.se/strang/omna/ http://www.smhi.se/cmp/jsp/polopoly.jsp ?d=5626&l=sv http://www.stralsakerhetsmyndigheten.s e/Allmanhet/UV--laser/

49 Appendix C: List of reference publications

COST Action 726 publications:

1. Gröbner, J., Hülsen, G., Vuilleumier, L., Blumthaler, M., Vilaplana, J. M., Walker D., Gill, J. E., Report of the PMOD/WRC Calibration and Intercomparison of Erythemal Radiometers , COST Office, 2009 2. Johnsen B., Kjeldstad B., Nakken Aalerud T., Tove Nilsen L., Schreder J., Blumthaler M., Bernhard G., Topaloglou C., Meinander O., Bagheri A., Slusser J. R., Davis J., Intercomparison of Global UV Index from Multiband Filter Radiometers: Harmonization of global UVI and spectral irradiance , GAW Report No. 179, WMO/TD-No. 1454, 2008 3. Koepke, P., De Backer, H., Bais, A., Curylo, A., Eerme, K., Feister, U., Johnsen, B., Junk, J., Kazantzidis, A. Krzyscin, J., Lindfors, A., Olseth, J., den Outer, P., Pribullova, A., Schmalwieser, A., Slaper, H., Staiger, H., Verdebout, J., Vuilleumier, L., Weihs, P., Modelling solar UV radiation in the past: Comparison of algorithms and input data, COST Action 726 Final Report, ISBN 978-92-898- 0043-3, COSt Office, 2008 4. Lity ńska Z., Koepke P., de Backer H., Gröbner J., Schmalwieser A., Vuilleumier L., Chubarova N., Feister U., Kaurola J., Kazantzidis A., Krzy ścin J., Lindfors A., den Outer P. N., Slaper H., Staiger H., Verdebout J. and Walker D., Final Scientific Report for COST Action726 “Long term changes and climatology of UV radiation over Europe, (prepared for publication) 5. Vilaplana J. M., Serrano A., Antón M., Cancillo M. L., Parias M., Gröbner J., Hülsen G., Zablocky G., Dıaz A., de la Morena B. A., Report of the “El Arenosillo”/INTA-COST Calibration and Intercomparison Campaign of UVER Broadband Radiometers . “El Arenosillo”, Huelva, Spain, 15 August – 21 September 2007’, ISBN 978-84-692-2640-7, COST Office 2009 6. Webb, A., Gröbner, J., Blumthaler, M., A practical guide to operating broadband instruments measuring erythemally weighted irradiance , ISBN 92-898-0032-1, COST Office, 2006

International reports:

1. IPCC (Intergovernmental Panel on Climate Change) , Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change , edited

50 by S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor, and H.L. Miller, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 2007, http://www.ipcc.ch/ipccreports/ar4-wg1.htm 2. UNEP (United Nations Environment Programme), Environmental effects of ozone depletion and the interaction with climate change: 2006 assessment , Nairobi, 2006, http://ozone.unep.org/Assessment_Panels/EEAP/eeap-report2006.pdf 3. WHO (World Health Organization), Global Solar UV Index, A practical Guide , ISBN 92 4 159007 6, Geneva, Switzerland, 2002, http://www.who.int/uv/publications/en/GlobalUVI.pdf 4. WHO (World Health Organization), Solar Ultraviolet radiation, Global burden of disease from solar ultraviolet radiation , ISBN 92 4 159440 3, Geneva, Switzerland, 2006, http://www.who.int/uv/health/solaruvradfull_180706.pdf 5. WMO (World Meteorological Organization), Scientific Assessment of Ozone Depletion: 2006, Global ozone Research and Monitoring Project , Report No. 50, Geneva, Switzerland, 2007, http://www.wmo.int/pages/prog/arep/gaw/ozone_2006/ozone_asst_report.html

References to paragraph 4: “Expectations for the future” published after the dates of international reports publication:

1. Angell, J.K., and M. Free, Ground-based observations of the slowdown in ozone decline and onset of ozone increase , J. Geophys. Res., 114 , D07303, doi:10.1029/2008JD010860, 2009 2. Comiso, J.C., C.L. Parkinson, R. Gersten, and L. Stock, Accelerated decline in the Arctic sea ice cover , Geophys. Res. Lett., 35 , L01703, doi:10.1029/2007GL031972, 2008 3. Eyring, V., D.W. Waugh, G.E. Bodeker, E. Cordero, H. Akiyoshi, J. Austin, S.R. Beagley, B.A. Boville, P. Braesicke, C. Brühl, N. Butchart, M.P. Chipperfield, M. Dameris, R. Deckert, M. Deushi, S.M. Frith, R.R. Garcia, A. Gettelman, M.A. Giorgetta, D.E. Kinnison, E. Mancini, E. Manzini, D.R. Marsh, S. Matthes, T. Nagashima, P.A. Newman, J.E. Nielsen, S. Pawson, G. Pitari, D.A. Plummer, E. Rozanov, M. Schraner, J.F. Scinocca, K. Semeniuk, T.G. Shepherd, K. Shibata, B. Steil, R.S. Stolarski, W. Tian, and M. Yoshiki, Multi-model projections of stratospheric ozone in the 21st century , J. Geophys. Res., 112 , D16303, doi:10.1029/2006JD008332, 2007

51 4. Overland, J.E., and M. Wang, Future regional Arctic sea ice declines , Geophys. Res. Lett., 34 , L17705, doi:10.1029/2007GL030808, 2007 5. Tourpali, K., A.F. Bais, A. Kazantzidis, C.S. Zerefos, H. Akiyoshi, J. Austin, C. Brühl, N. Butchart, M.P. Chipperfield, M. Dameris, M. Deushi, V. Eyring, M.A. Giorgetta, D.E. Kinnison, E. Mancini, D.R. Marsh, T. Nagashima, G. Pitari, D.A. Plummer, E. Rozanov, K. Shibata, and W. Tian, Clear sky UV simulations in the 21st century based on Ozone and Temperature Projections from Chemistry- Climate Models , Atmos. Chem. Phys. Disc., 9 (4), 1165-1172, 2009 6. Waugh, D.W., L. Oman, S.R. Kawa, R.S. Stolarski, S. Pawson, A.R. Douglass, P.A. Newman, and J.E. Nielsen, Impacts of climate change on stratospheric ozone recovery , Geophys. Res. Lett., 36 , 2009 7. Yang, E.S., D.M. Cunnold, M.J. Newchurch, R.J. Salawitch, M.P. McCormick, J.M. Russell, III, J.M. Zawodny, and S.J. Oltmans, First stage of Antarctic ozone recovery , J. Geophys. Res., 113 , 2008

52