Earth System Science Education

EarthWhat System is Earth SystemScience Science?

• Earth system science provides a physical basis for AirAir understanding the world in which we live and upon which humankind seeks to achieve sustainability

• Earth system science embraces chemistry, physics, biology,

Water mathematics and applied sciences in transcending disciplinary boundaries to treat the Earth as an integrated system

• Earth system science has been stimulated by the the increasing role of human activity in global change and the capabilities Land of global monitoring of the Earth from space

• Earth system science seeks a deeper understanding of the physical, chemical and biological interactions that determine the Life past, current and future states of the Earth

See also http://www.usra.edu/esse/summer98/oneminuteess.html and http://www.usra.edu/esse/essonline/whatis.html M. Ruzek, 2007 Earth System Science Education

The “Bretherton Report”

Goal: To obtain a scientific

AirAir understanding of the entire Earth System on a global scale by describing how its

Water component parts and their interactions have evolved, how they function, and how they may be expected to Land continue to evolve at all time scales.

Life Report of the Earth System Sciences Committee of the NASA Advisory Council

January, 1988 The Bretherton Diagram- Complex

Mitchell K. Hobish, Earth Systems Science, Section 16, Remote Sensing Tutorial http://rst.gsfc.nasa.gov/Sect16/Sect16_3.html Earth System Science Education

The Bretherton Diagram Simplified

Physical Climate System

Climate AirAir Atmospheric Physics/Dynamics Change

Terrestrial Ocean Dynamics Energy/Moisture Human Water Activities Global Moisture Soil CO2

Marine Terrestrial Land Land Biogeochemistry Ecosystems Use

Tropospheric Chemistry CO2

Biogeochemical Cycles Pollutants Life (from Earth System Science: An Overview, NASA, 1988) Earth System Science Education

ESS Builds on the Disciplines

AirAir

Water

Land

Life Geospheres

Atmosphere

Anthroposphere

Biosphere Hydrosphere

Lithosphere and Pedosphere Geography and Earth System Science

Earth System Science is inherently spatial. It uses many scales space (from the particle to global) and in time.

The interdisciplinary nature of the science and its focus on connections between systems makes it attractive to geographers. Mitchell K. Hobish, Earth Systems Science, Section 16, Remote Sensing Tutorial http://rst.gsfc.nasa.gov/Sect16/Sect16_3.html Earth Systems Science is the study of:

• Interactions between oceans, atmosphere, living things, geologic processes, land surface dynamics, and human systems. • Processes that connect biological, physical, and human systems operating near the Earth's surface. • How interrelationships between physical and biological systems impact each other and lead to changes. How is ESS different from other types of science?

• ESS deals with the relationships between physical and biological systems instead of the systems themselves. • Earth System Science uses holistic rather than reductionist approaches. • Earth System Science is interdisciplinary, including many academic disciplines No single discipline can fully address the scope of ESS. Earth Systems Science • A prime focus of Earth System Science is the study of past and future changes in Earth systems: Paleoclimate, Global warming. Strategies have been developed to address climate change. • Special attention is paid to how human activities lead to changes in linkages between systems and the response from humans to those changes: “Global Change” research. • ESS studies many different systems, each defined by its own sets of characteristics and subsystems. Physical systems: atmospheric chemistry, cryosphere, hydrosphere, energy transfer. Biological systems: marine life, terrestrial ecosystems, biogeochemistry. Humans: land use, atmospheric changes. External forces: volcanism, sun, solar system (orbital mechanics, impacts). Surv Geophys (2012) 33:413–426 415

Fig. 1 The global annual mean earth’s energy budget for 2000–2005 (W m-2). The broad arrows indicate the schematic flow of energy in proportion to their importance. Adapted from Trenberth et al. (2009) with changes noted in the text Trenberth et al. (2009), below. Uncertainties are discussed in Trenberth et al. (2009) andTrenberth are mostly notand dealt Fasullo with (2012) here, except to highlight some sources of discrepancy with other studies. In Fig. 1, use has been made of conservation of energy and the assumption that, on a time scale of years, the change in heat storage within the atmosphere is very small. Accordingly, the net radiation at TOA RT is the sum of the ASR minus the OLR: RT = ASR - OLR. In turn, the ASR is the difference between the incoming solar radi- ation and the reflected solar radiation. At the surface, the ASR has to be offset by the sensible heat and latent heat fluxes plus the net longwave radiation. The latter is made up of two large terms: the emitted radiation from the surface and the downwelling longwave radiation coming back from the atmosphere. Both at the surface and TOA the imbalance is the same and, as noted above, is estimated to be 0.9 W m-2. Updates in Trenberth et al. (2009) included revised absorption in the atmosphere by water vapor and aerosols, since Kim and Ramanathan (2008) found that updated spec- troscopic parameters and continuum absorption for water vapor increased the absorption by 4–6 W m-2. The sensible heat has values of 17, 27, and 12 W m-2 for the globe, land, and ocean (just over 70% of the Earth), and, even with uncertainties of 10%, the errors are only order 2 W m-2. There is widespread agreement that the global mean surface upward longwave (LW) radiation is about 396 W m-2, which is dependent on the skin temperature and surface emissivity (Zhang et al. 2006). Global precipitation should equal global evaporation for a long-term average, and estimates are likely more reliable of the former. However, there is considerable uncertainty in precipitation over both the oceans and land (Trenberth et al. 2007b; Schlosser and Houser 2007). The latter is mainly due to wind effects, undercatch, and sampling, while the

123

Equator-to-pole radiation imbalance drives the atmospheric general circulation, and the oceanic thermohaline circulation Climate Change Definition • Climate Change is a change in the statistical distribution of weather over a period of time beyond the seasonal cycle, ranging from years, decades to millions of years. It can be a change in the average weather or a change in the distribution of weather events around an average. • Climate change may happen over a specific region, or may occur across the whole earth system • Greenhouse warming refers to a kind of climate change forced by anthropgenic well-mixed greenhouse gases

(CO2, CH4 N2O…) associated with modern climate change, since approximately 150 years ago. • Natural (Climate) Variability/Oscillations ( MJO, ENSO, QBO, PDO, AO, AMO, Multi-decadal, volcanic eruption, solar variability…) 14

The Keeling Curve

Δ ~ +40% for CO2, +200% for CH4, + 40% for N2O IPCC 2013 Study the Earth as a Dynamical System: Climate Feedback Factor (F)

ΔT Forces acting on Earth system the Earth system response IMPACTS

ΔT’=ΔT + f x ΔT’

f xΔT’ Feedback Of the total forcing of the climate system, 40% is due to the direct effect of greenhouse gases and aerosols, and 60% is from feedback effects, such as increasing concentrations of water vapor as temperature rises. Climate Change Attribution and Projection are Challenging

- Climate Change = Response to anthropogenic forcing + Natural Variability (ENSO, PDO, NAO…, volcanic eruptions, solar cycle…) + Noise - Lack of reliable long-term data records for validation - Rely on model simulations, and projections; large model uncertainties - Validation: Singular imperfect real world realization vs. ensemble of imperfect model projections

How is Earth System Science performed?

• Earth system is a network of self-organizing systems connected by flows of gases, energy, and nutrients. • In ESS, past and present interdisciplinary observations are needed, • hierarchical models constrained by observations are essential to describe connections between biological, physical, and human systems, and make projections of the future. • Remote Sensing Observations (sustained satellite missions), Field Campaigns, Modeling, and Society Applications are the four pillars of NASA’s Earth System Science program.

Evolution of Weather and Climate Computer (Mathematical) Models (1950 to present)

Barotropic Shallow Water models (1950-70’s) à baroclinic two-layer models (1960-80’s) à Atmospheric General Circulation models (1970..) à Global Numerical Weather Prediction Models (1970…) à Coupled Ocean-Land Atmosphere global climate models (1980…)à Cloud Resolving models/High Resolution Regional Climate Models (1990-present) à Cloud permitting, variable Earth System Models (atmosphere, hydrosphere, biosphere, cryosphere, anthroposphere, 1990…) Earth System Science Education

AirAir

Water

Land

Life Earth System Science Education

AirAir

Water

Land

Life Priority Science Questions

Ø How is the global Earth system changing?

Ø What are the primary forcings of the Earth system?

Ø How does the Earth system respond to natural and human-induced changes?

Ø What are the consequences of changes in the Earth system for human civilization?

Ø How well can we predict future changes to the Earth system?

Underground Water

Water stored in soil and aquifers below Earth's hydrological data has led to the development surface is very sparsely measured worldwide. of a more efcient and sustainable approach Before GRACE, hydrologists were skeptical if to water management. [Above] NASA and the German they would be able to use the data to reveal Aerospace Center (DLR) collaborated to design and unknown groundwater depletion. However, Dry soils can add to drought risk or increase launch GRACE. NASA provided over the last decade, by measuring mass the length of a drought. To help monitor the satellites; developed the changes with GRACE, scientists from NASA, these changes, NASA provided data on deep instruments and some of the satellite components; maintained and around the world, have found more and soil moisture and groundwater from GRACE overall mission management, data more locations where humans are pumping to the National Drought Mitigation Center validation and storage; and has out groundwater faster than it is replenished. each week, using a hydrology model to responsibility for the science data products. The DLR provided the For example, in 2015, a team of researchers calculate how the moisture was changing launch services and operations published a comprehensive survey showing throughout the month between one map activities. The science data products a third of Earth's largest groundwater basins and the next. Te data were used to prepare are produced at CSR, GFZ and JPL. are being rapidly depleted. Adding the weekly maps of U.S. drought risk. Image credit: Astrium/GFZ GRACE data to other existing sources of continued on next page

Image credit: NASA's Scientific Visualization Studio [Above] The gravity variations measured by GRACE can be used to determine water storage on land. By comparing current data to an average over time, scientists can generate an anomaly map to see where terrestrial water storage has decreased or increased. This map, created using GRACE data, shows the global terrestrial water storage anomaly in April 2015, relative to the 2002-2015 mean. Rust colored areas show areas where water has decreased, and areas in blue are where water levels have increased. Note the significant decreases in water storage across most of California are related to groundwater, while decreases along the Alaska coastline are due to glacier melt.

GRACE-FO I Gravity Recovery and Climate Experiment Follow-On 5 Educating for the End-to-End Information Flow

Calibration, Transformation Interaction Between Interactive To Characterized Dissemination 15 Geophysical Parameters Modeling/Forecasting Petabytes 10 and Observation Multi-platform, multi- Systems Predictions parameter, high spatial and Terabytes 1012 temporal resolution, remote & in-situ sensing Gigabytes 109 Megabytes 106 Information Advanced Sensors Data Processing & Analysis Synthesis Access to Knowledge

WET

VERY DRY DRY WET WET DRY DRY VERY WET Supplementary Materials

The Stratosphere: Ozone Loss

• Total Ozone Mapping Spectrometer (TOMS Series, OMI) 1991… Antarctic Ozone • Science Amounts 1979 – Long term trends in ozone – Ozone hole development & trends

Earth Probe TOMS 120 Total Ozone 500 Dobson Units

2001 Ozone Hole: The World Avoided by the Montreal Protocol

Newman et al., 2009, ACP The Melting of the Arctic Sea Ice Key findings from Arctic Monitoring and Assessement Program: - The past 10 years (2005-2015) make up the warmest period ever recorded in the region, and these warm temperatures are causing major changes in he Arctic environement. - The largest and most permanent bodies of ice in the Arctic, including multi-year sea ice, mountain glaciers, and the Greenland ice sheet, have melted faster since 2000 than in the previous decade. (The Greenland work was also the topic of a recent image of the day.) - Model results reported in the last IPCC report underestimated how quickly sea ice is changing. - The Arctic Ocean will be nearly ice-free during the summer within this century, probably within the next 30-40 years. - Changes in the Arctic snow and ice fundamentally change ecosystems, destroying some habitats, which will impact Arctic infrastructure, society and peoples. - Loss of snow and ice and the release of greenhouse gases (CH4, in particular) from melting permafrost will enhance global warming. - Melting glaciers and ice sheets contributed more than 40 percent of the global sea level rise (about 3 mm per year) between 2003 and 2008. Further melting will contribute substantially to the 0.9 to 1.6 meter sea-level rise expected by 2100. Trans-Pacific Aerosol Transport

Aerosol transport across the Pacific Ocean, using AVHRR data (after Husar et al. 2000).

Starting on 15 April 1998, a fierce dust storm (left) originated in the Northwest swept through China, downing electrical wires, sparking forest fires and snarling air traffic and causing serious environmental and health hazards (after CNN). Kosa: 1998 Events

In mid-April, 2001, 2.5E8 metric tons of dust were emitted from Asian. The amount of Asian dust in the continental US ABL was 1.1E5 metric ton, a value comparable to the daily emission of all US sources of particulate matter less than 10 micron (PM10). D. Jaffe et al (EOS, 2003) Aerosol Index SeaWiFS: April 9, 2001

τ(dust) - red

τ( pollution) - green

MODIS: March 20, 2001

Dust streak over Korea REPORTS

– mass ratio on discharge and charge is 2e /O2, 3. G. Girishkumar, B. McCloskey, A. C. Luntz, S. Swanson, 22. Y.-C. Lu, H. A. Gasteiger, Y. Shao-Horn, J. Am. Chem. Soc. confirming that the reaction is overwhelmingly W. Wilcke, J. Phys. Chem. Lett. 1,2193(2010). 133,19048(2011). 4. B. Scrosati, J. Hassoun, Y.-K. Sun, Energy Environ. Sci. 23. T. Ogasawara, A. Débart, M. Holzapfel, P. Novák, Li2O2 formation/decomposition. We have also 4,3287(2011). P. G. Bruce, J. Am. Chem. Soc. 128,1390(2006). shown that such electrodes are particularly effec- 5. J.-G. Zhang, P. G. Bruce, X. G. Zhang, in Handbook of 24. B. D. McCloskey et al., J. Am. Chem. Soc. 133,18038(2011). tive at promoting the decomposition of Li2O2, Battery Materials, C. Daniel, J. O. Besenhard, Eds. 25. S. J. Visco, B. D. Katz, Y. S. Nimon, L. D. DeJonghe, (Wiley-VCH, Weinheim, Germany, ed. 2, 2011), pp. 759–811. U.S. Patent 7,282,295 (2007). with all the Li2O2 being decomposed below 4 V and ~50% decomposed below 3.3 V, at a rate ap- 6. J. Christensen et al., J. Electrochem. Soc. 159, R1 (2012). 26. X.-H. Yang, P. He, Y.-Y. Xia, Electrochem. Commun. 11, 7. S. A. Freunberger et al., J. Am. Chem. Soc. 133,8040 1127 (2009). proximately one order of magnitude higher than (2011). 27. J. Read, J. Electrochem. Soc. 149,A1190(2002). on carbon. Although DMSO is not stable with 8. F. Mizuno, S. Nakanishi, Y. Kotani, S. Yokoishi, H. Iba, 28. Y. G. Wang, H. S. Zhou, J. Power Sources 195,358(2010). bare Li anodes, it could be used with protected Li Electrochemistry 78,403(2010). 29. J. S. Hummelshøj et al., J. Chem. Phys. 132,071101 anodes. Nanoporous Au electrodes are not suit- 9. W. Xu et al., J. Power Sources 196,3894(2011). (2010). 10. G. M. Veith, N. J. Dudney, J. Howe, J. Nanda, J. Phys. 30. V. S. Bryantsev, M. Blanco, F. Faglioni, J. Phys. Chem. A able for practical cells, but if the same benefits Chem. C 115,14325(2011). 114,8165(2010). could be obtained with Au-coated carbon, then 11. B. D. McCloskey, D. S. Bethune, R. M. Shelby, G. Girishkumar, 31. Y. Mo, S. P. Ong, G. Ceder, Phys. Rev. B 84,205446(2011). low-mass electrodes would be obtained, although A. C. Luntz, J. Phys. Chem. Lett. 2, 1161 (2011). 32. D. Aurbach, M. Daroux, P. Faguy, E. Yeager, cost may still be a problem. A cathode reaction 12. S. A. Freunberger et al., Angew. Chem. Int. Ed. 50, J. Electroanal. Chem. 297,225(1991). 33. J. Hassoun, F. Croce, M. Armand, B. Scrosati, Angew. Chem. overwhelmingly dominated by Li O formation 8609 (2011). 2 2 13. H. Wang, K. Xie, Electrochim. Acta 64, 29 (2012). Int. Ed. 50,2999(2011). on discharge, its complete oxidation on charge 14. H.-G. Jung, J. Hassoun, J.-B. Park, Y.-K. Sun, B. Scrosati, and sustainable on cycling, is an essential pre- Nat. Chem. 4,579(2012). Acknowledgments: P.G.B. is indebted to the UK Engineering requisite for a rechargeable nonaqueous Li-O 15. Materials and methods are available as supplementary and Physical Sciences Research Council, including the 2 Supergen Programme and Alistore for financial support. battery. Hence, the results presented here encour- materials on Science Online. 16. C. O. Laoire, S. Mukerjee, K. M. Abraham, E. J. Plichta, Supplementary Materials age further study of the rechargeable nonaqueous M. A. Hendrickson, J. Phys. Chem. C 114,9178(2010). www.sciencemag.org/cgi/content/full/science.1223985/DC1 Li-O cell, although many challenges to practical 17. Z. Peng et al., Angew. Chem. Int. Ed. 50,6351(2011). 2 Materials and Methods 18. B. D. McCloskey et al., J. Phys. Chem. Lett. 3, 997 (2012). devices remain. Figs. S1 to S9 19. A. Débart, A. J. Paterson, J. Bao, P. G. Bruce, Angew. References (34, 35) References and Notes Chem. Int. Ed. 47,4521(2008). 1. K. M. Abraham, Z. Jiang, J. Electrochem. Soc. 143, 1 (1996). 20. C. J. Allen, S. Mukerjee, E. J. Plichta, M. A. Hendrickson, 30 April 2012; accepted 26 June 2012 2. P. G. Bruce, S. A. Freunberger, L. J. Hardwick, K. M. Abraham, J. Phys. Chem. Lett. 2,2420(2011). Published online 19 July 2012; J.-M. Tarascon, Nat. Mater. 11, 19 (2012). 21. Y.-C. Lu et al., Energy Environ. Sci. 4,2999(2011). 10.1126/science.1223985 on August 29, 2016

aerosol intercontinental transport on seasonal Aerosols from Overseas Rival and annual time scales (11, 12 ). We integrated satellite measurements from the Moderate-resolution Imaging Spectroradiometer REPORTS Domestic Emissions over North America (MODIS) (13 )andtheCloud-AerosolLidarwith Orthogonal Polarization (CALIOP) (14 )inorder Hongbin Yu,1,2* Lorraine A. Remer,3 Mian Chin,2 Huisheng Bian,2,3 Qian Tan,2,4 To demonstrate the impact of these imported to characterize the three-dimensional distribu- Tianle Yuan,2,3 Yan Zhang2,4 particles on North American regional climate, we tions of trans-Pacific dust transport (15 ). We used MODIS measurements of total AOD and fine- estimated the direct radiative effect (DRE) over http://science.sciencemag.org/ North America contributed by the imports (15 ). Many types of aerosols have lifetimes long enough for their transcontinental transport, making mode fraction over ocean to separate AOD for To do so, we had to characterize the evolution of them potentially important contributors to air quality and climate change in remote locations. We dust, combustion aerosol, and marine aerosol (16 ). the imported aerosol amount over the continent estimate that the mass of aerosols arriving at NorthAmericanshoresfromoverseasiscomparable Combustion aerosol refers to aerosol products with the total mass of particulates emitted domestically. Curbing domestic emissions of particulates from the burning of both biomass and fossil fuels, itself rather than the ocean, and we did this by and precursor gases, therefore, is not sufficient to mitigate aerosol impacts in North America. which include sulfates, nitrates, and carbona- using GOCART and GMI results of source- The imported contribution is dominated by dust leaving Asia, not by combustion-generated ceous particles. The partitioning of AOD into receptor relationship experiments (15 ). Aerosol particles. Thus, even a reduction of industrial emissions of the emerging economies of Asia could these three categories accounts for fine-mode optical properties were characterized according be overwhelmed by an increase of dust emissions due to changes in meteorological conditions components of marine and dust aerosol (15 , 16 ). Downloaded from to the Aerosol Robotic Network (AERONET) and potential desertification. The CALIOP measurements are used to char- measurements (24 ). Collectively, the imported acterize seasonal variations of aerosol extinction pollution and dust introduces a reduction of tmospheric aerosols emitted or produced mote international sources. Assessing the aerosol profiles, with dust being separated from other cloud-free net solar radiation of –1.7 [–1.5, –1.9] in one region can be transported thou- intercontinental transport and its impacts on at- types of aerosols by the measured depolarization −2 Asands of miles downwind to affect other mospheric composition, air quality, and climate ratio (15 ). The climatology of springtime (March- and –3.0 [–2.6, –3.4] Wm at top-of-atmosphere regions on intercontinental or hemispheric scales in North America is thus needed from both sci- April-May, or MAM) AOD (2001–2007) and (TOA) and surface, respectively, which repre- (1–3 ). Because of such intercontinental transport, entific and policy perspectives. Currently, such vertical profile of extinction (2006–2010) over sents 31% (24 to 40%) and 37% (28 to 48%) of emission controls over North America may be assessment for the most part has been based on the North Pacific basin are shown in Fig. 1. Spring the total DRE over North America (Fig. 4). In offset partly by the import of aerosols from re- global model simulations (4 –6 )andremainsvery is the most active season for trans-Pacific trans- spring, the imported aerosols make the greatest uncertain (7 ). port of combustion aerosols and dust because Today’sconstellationofpassiveandactive of the combined effect of active extratropical cy- contribution to the DRE (fig. S5). DRE by the 1Earth System Science Interdisciplinary Center, University of imported pollution accounts for as much as 31 Maryland, College Park, MD 20740, USA. 2Earth Science Di- satellite sensors are providing three-dimensional clones and the strongest mid-latitude westerlies. rectorate, NASA Goddard Space Flight Center, Greenbelt, MD distributions of aerosol properties on a global However, trans-Pacific transport occurs through- to 59% of that by the imported dust, although 20771, USA. 3Joint Center for Earth Systems Technology, Uni- scale, with improved accuracy for aerosol optical out the year (12 ). Over the period we examined the imported dust mass is an order of magni- versity of Maryland at Baltimore County, Baltimore, MD 21228, 4 depth (AOD) and enhanced capability of char- here, interannual variations of AOD are generally tude larger than the imported pollution aerosol USA. Goddard Earth Sciences Technology and Research Cen- ter, Universities Space Research Association, Columbia, MD acterizing aerosol type (8 ). Such advances have small for dust in the outflow and inflow regions mass. This is because the combustion aerosols 21044, USA. made it feasible to elucidate the evolution of aero- (8 and 4%, respectively), but larger (17 and 18%, scatter and absorb the solar radiation in a more *To whom correspondence should be addressed. E-mail: sol plumes during the cross-ocean transport (9 , 10 ) respectively) for combustion aerosol. The rela- effective way than does dust. Besides the aero- [email protected] and generate measurement-based estimates of tively large interannual variations on August 29, 2016 for combustion sol DREs discussed above, the imported aerosols could exert substantial effects in many other 566 3AUGUST2012 VOL337 SCIENCE www.sciencemag.org ways, such as changing atmospheric stability Fig. 2. (A)Satellite-basedestimateofdustmassfluxinEastAsiaoutflowandNorthAmericainflow.(B) by absorbing solar radiation (25 , 26 ), altering The import of aerosols to North America is 64 Tg/a, including trans-Pacific dust and pollution aerosols and cloud and precipitation processes through trans-Atlantic dust, is comparable with (C)theannualemissionsandproductionsofaerosolsof69Tg/a acting as ice nuclei (27 ), and accelerating the from major domestic sources in North America. Primary PM emissions include only anthropogenic sources melting of snow in the Sierra Nevada by dep- (excluding prescribed fires). osition on snow (28 ). In comparison, the imported aerosols would have less substantial impacts on air quality of Yu et al., Science 2012

North America. Although the domestic emis- http://science.sciencemag.org/ sions are all near the surface, the imported aero- sols are predominantly above the boundary layer, as previously noted. So dust may substantially affect near-surface aerosol concentrations only in parts of the western United States and Canada and on an episodic basis. In other regions, curb- ing domestic emissions should still be the most efficient way for controlling air pollution (5 ). Downloaded from This differs from imported ozone, which has lon- ger lifetime than aerosols and can continuously form via photochemistry during oceanic transport. Because of the long-range transport, dust makes a substantial contribution to AOD away from strong anthropogenic sources, as noted in Fig. 1. Interpretation of AOD for a variety of ap- plications, including aerosol-cloud interaction, should consider the possibility of a substantial portion of dust in the mix. Clearly assessing and mitigating the impacts of imported aerosols requires a modeling sys- tem that links the local, regional, intercontinen- tal, and global scales. Satellite measurements as discussed in this study provide an observational Fig. 3. Comparisons of satellite (MODIOP) and model (GOCART and GMI) estimates of dust export flux benchmark to evaluate and constrain the model from the Asian continent (A and C)anddustimportfluxtoNorthAmerica(B and D). Meridionally simulations. Although this study focuses on the integrated dust mass fluxes are shown in (A) and (B) with seasonal distinction, and meridional dis- impacts of intercontinental transport into North tributions of seasonal dust mass fluxes are shown in (C) and (D), with boxes and error bars representing America, aerosols emitted and produced in North mean and range of seasonal mass flux, respectively.

568 3AUGUST2012 VOL337 SCIENCE www.sciencemag.org Newtonian vs. Darwinian Perspective of Science Physics Ecology The more you look The more you look the simpler it gets the more complex it gets Primacy of Primacy of contingency and Initial conditions complex historical factors Universal patterns; Weak trends; search for laws reluctance to seek laws Predictive Mostly descriptive, explanatory (chaos and quantum explanatory mechanics notwithstanding)

Central role for ideal Disdain for caricatures of Systems (ideal gas, nature harmonic oscillator) [Harte, 2002, Phys. Today]