DOCSLIB.ORG

SI Traceability and Scales for Underpinning Atmospheric

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
SI Traceability and Scales for Underpinning Atmospheric Metrologia PAPER Recent citations SI traceability and scales for underpinning - Amount of substance and the mole in the SI atmospheric monitoring of greenhouse gases Bernd Güttler et al - Advances in reference materials and To cite this article: Paul J Brewer et al 2018 Metrologia 55 S174 measurement techniques for greenhouse gas atmospheric observations Paul J Brewer et al - News from the BIPM laboratories—2018 Patrizia Tavella et al View the article online for updates and enhancements. This content was downloaded from IP address 205.156.36.134 on 08/07/2019 at 18:02 IOP Metrologia Bureau International des Poids et Mesures Metrologia Metrologia Metrologia 55 (2018) S174–SS181 https://doi.org/10.1088/1681-7575/aad830 55 SI traceability and scales for underpinning 2018 atmospheric monitoring of greenhouse © 2018 BIPM & IOP Publishing Ltd gases MTRGAU Paul J Brewer1,6 , Richard J C Brown1 , Oksana A Tarasova2, Brad Hall3, George C Rhoderick4 and Robert I Wielgosz5 S174 1 National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, United Kingdom 2 World Meteorological Organization, 7bis, avenue de la Paix, Case postale 2300, CH-1211 Geneva 2, Switzerland 3 National Oceanic and Atmospheric Administration, 325 Broadway, Mail Stop R.GMD1, Boulder, CO 80305, United States of America P J Brewer et al 4 National Institute of Standards and Technology, 100 Bureau Drive, MS-8393 Gaithersburg, MD 20899-8393, United States of America 5 Printed in the UK Bureau International des Poids et Mesures, Pavillon de Breteuil, F-92312 Sèvres Cedex, France E-mail: [email protected] MET Received 21 June 2018, revised 2 August 2018 Accepted for publication 6 August 2018 10.1088/1681-7575/aad830 Published 7 September 2018 Abstract Paper Metrological traceability is the property of a measurement result whereby it can be related to a stated reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty. The stated reference can be the International System of Units, and 1681-7575 more specifically a realisation of a primary standard with its value and uncertainty expressed in SI units, which offers many benefits such as long term stability and the ability to reproduce the standard within its stated uncertainty at any time. Alternatively, measurements can be 5 made traceable to an empirical scale, an approach that has evolved for practical reasons to meet the needs of certain measurement communities. We explore the benefits and drawbacks of these two measurements systems as they have evolved for greenhouse gas measurements S174 at background levels and outline the advantages of using elements from each to secure a more robust measurement infrastructure. In particular, this work examines the importance S181 of compatibility, the accuracy of measurement results and the benefits of comparisons with independent primary standards. Keywords: metrology, traceability, calibration, SI, scale, atmospheric monitoring Introduction the measurement uncertainty. The reference in a measurement system, to which measurements are made traceable, can be The goal of implementing metrological traceability within a realised in different ways. Here we consider two approaches measurement system, is to ensure that measurements can be for a measurement system for greenhouse gas amount-of-sub- comparable and compatible anywhere at any time [1]. A met- stance fractions in the atmosphere. The first provides trace- rological traceability chain [1] must be established from the ability to the international system of units (SI) and the second (value of the) measurement result to the value embodied in, or to a defined scale. In particular, we consider the advantages carried by a material, or obtained by a measurement procedure and disadvantages of each approach and how the measure- [1]. Metrological traceability is not just a simple statement ment system may ultimately benefit from an approach that [2]. It must be based on an unbroken chain of quantity values combines elements of each. in a specified material or measurement, each contributing to There are some prominent examples of the use of scales within metrology, for example for temperature measurements 6 Author to whom any correspondence should be addressed. 1681-7575/18/05S174+8$33.00 S174 © 2018 BIPM & IOP Publishing Ltd Printed in the UK Metrologia 55 (2018) S174 P J Brewer et al [3]. The unit of the fundamental physical quantity known as statement will include all sources of uncertainty, up to and thermodynamic temperature (T), is the kelvin (K), defined as including the realisation of the SI units themselves. The the fraction 1/273.16 of T at the triple point of water. Triple- degree of equivalence of measurement standards can then be point-of-water cells provide a convenient realisation of this calculated by the difference in their values, to the extent to definition. For temperatures other than the triple point of which this difference is smaller than the combined uncertain- water, direct measurements of thermodynamic temperature ties of the values of the standards. require a primary thermometer based on a well-understood In the field of gas analysis, reference materials are usu- physical system whose temperature may be derived from ally disseminated in high pressure cylinders using gravimetric measurements of other quantities. In practice, primary ther- methods to assign the reference value. There is a broad con- mometry is difficult and time consuming and not a practical sensus amongst metrologists that ‘verification’ is required to means of disseminating K. As an alternative, the International ensure the ‘primary method’ is behaving as expected [7]. The Temperature Scale provides an internationally accepted recipe implication is that within gas metrology, amount-of-substance for realising temperature in a practical way. The present fraction values can be realised and their uncertainties calcu- scale is the International Temperature Scale of 1990 (ITS- lated with traceability to the mole. This is achieved via mass 90) (Recommendation 5, CI-1989). The values assigned to and purity measurements, tables of atomic weights and the the fixed-point temperatures used in ITS-90 and pre-ITS-90 molar mass constant Mu. These values should then be verified scales were based on the state-of-the-art knowledge of T at by comparison against an independently prepared gas mixture the time of inception of each scale. Estimates of the differ- of similar composition. This process is intended to demon- ences between T and the ITS-90 (T90) are available with strate that errors in preparation, loss of material to cylinder consensus estimates provided for T − T90, for selected meas- walls, and reaction of gaseous components within the mixture, urements from 4.2 K to 1358 K, as well as a recommendation which would compromise the ‘complete understanding’ of the for analytic approximations to T − T90 for the range 0.65 K to method are well understood. It is agreed that this verification 1358 K. The values of T − T90 are small, and would be neg- step provides a good demonstration that the value and uncer- ligible for the vast majority of users. Considerable research tainty have been properly assigned, based on a gravimetric activities have gone into understanding the factors that can value fully traceable to the SI [8]. The general methods for lead to variations in the fixed points (e.g. impurities and iso- the realisation of gas standards with assigned amount-of- topic composition), so that the scales can be realised inde- substance fractions is described within the written standard pendently in National Metrology Institutes (NMIs) around ISO 6142-1:2015 [8]. This methodology has been success- the world achieving comparable results. As will be explained fully used by NMIs to develop standards for greenhouse gases later, this differs from the scale approach developed for green- for different measurement communities from emission levels house gases, where the scale is realised by one unique set of down to background atmospheric levels and below. Standards standards, held by one institute. produced by such methods can routinely be offered with rela- tive standard uncertainties of 0.1%, but for special applica- tions and over particular amount-of-substance fraction ranges Discussion these can be reduced to 0.025% or below. Traceability to the SI for the amount-of-substance fraction of greenhouse gases in air The scale approach The role of a NMI is to provide national standards for mea- An alternative approach is a measurement system based on surement and in many cases manage the national measure- traceability to a ‘scale’, often a family or collection of gas ment system comprising calibration laboratories, certification standards, based on an agreed reference value or reference and accreditation bodies, and legal metrology [4]. It is also method. This system offers superior precision as compariso ns to carry out the necessary comparisons with other NMIs, are made to one source and the absolute accuracy of the now through the International Committee for Weights and artefact has limited impact on measurement compatibility, Measures’ Mutual Recognition Arrangement (CIPM-MRA) provided that all measurements are traceable to the same ref- [5], to demonstrate international equivalence of the national erence, and that reference is stable. Within the greenhouse standards. In most cases this is based on their traceability to the gas field (particularly at the global scale), this practice arose SI. This system was adopted at the 10th General Conference partially out of the realisation that gas amount-of-substance on Weights and Measures (CGPM) on which to establish a fraction measurements could be performed with precisions practical system of measurement for international use [6]. that were often better than the uncertainties associated with Today the SI is the fixed reference point for almost all modern gas mixture preparation. In addition, the key quantity to be science and technology. The base units are regarded as dimen- measured was the relative difference in amount-of-substance sionally independent and form a coherent set of derived units.
Load more

Recommended publications
  • Climate Change: How Do We Know We're Not Wrong? Naomi Oreskes
    Changing Planet: Past, Present, Future Lecture 4 – Climate Change: How Do We Know We’re Not Wrong? Naomi Oreskes, PhD 1. Start of Lecture Four (0:16) [ANNOUNCER:] From the Howard Hughes Medical Institute...The 2012 Holiday Lectures on Science. This year's lectures: "Changing Planet: Past, Present, Future," will be given by Dr. Andrew Knoll, Professor of Organismic and Evolutionary Biology at Harvard University; Dr. Naomi Oreskes, Professor of History and Science Studies at the University of California, San Diego; and Dr. Daniel Schrag, Professor of Earth and Planetary Sciences at Harvard University. The fourth lecture is titled: Climate Change: How Do We Know We're Not Wrong? And now, a brief video to introduce our lecturer Dr. Naomi Oreskes. 2. Profile of Dr. Naomi Oreskes (1:14) [DR. ORESKES:] One thing that's really important for all people to understand is that the whole notion of certainty is mistaken, and it's something that climate skeptics and deniers and the opponents of evolution really exploit. Many of us think that scientific knowledge is certain, so therefore if someone comes along and points out the uncertainties in a certain scientific body of knowledge, we think that undermines the science, we think that means that there's a problem in the science, and so part of my message is to say that that view of science is incorrect, that the reality of science is that it's always uncertain because if we're actually doing research, it means that we're asking questions, and if we're asking questions, then by definition we're asking questions about things we don't already know about, so uncertainty is part of the lifeblood of science, it's something we need to embrace and realize it's a good thing, not a bad thing.
    [Show full text]
  • CO2, Hothouse and Snowball Earth
    CO2, Hothouse and Snowball Earth Gareth E. Roberts Department of Mathematics and Computer Science College of the Holy Cross Worcester, MA, USA Mathematical Models MATH 303 Fall 2018 November 12 and 14, 2018 Roberts (Holy Cross) CO2, Hothouse and Snowball Earth Mathematical Models 1 / 42 Lecture Outline The Greenhouse Effect The Keeling Curve and the Earth’s climate history Consequences of Global Warming The long- and short-term carbon cycles and silicate weathering The Snowball Earth hypothesis Roberts (Holy Cross) CO2, Hothouse and Snowball Earth Mathematical Models 2 / 42 Chapter 1 Historical Overview of Climate Change Science Frequently Asked Question 1.3 What is the Greenhouse Effect? The Sun powers Earth’s climate, radiating energy at very short Earth’s natural greenhouse effect makes life as we know it pos- wavelengths, predominately in the visible or near-visible (e.g., ul- sible. However, human activities, primarily the burning of fossil traviolet) part of the spectrum. Roughly one-third of the solar fuels and clearing of forests, have greatly intensifi ed the natural energy that reaches the top of Earth’s atmosphere is refl ected di- greenhouse effect, causing global warming. rectly back to space. The remaining two-thirds is absorbed by the The two most abundant gases in the atmosphere, nitrogen surface and, to a lesser extent, by the atmosphere. To balance the (comprising 78% of the dry atmosphere) and oxygen (comprising absorbed incoming energy, the Earth must, on average, radiate the 21%), exert almost no greenhouse effect. Instead, the greenhouse same amount of energy back to space. Because the Earth is much effect comes from molecules that are more complex and much less colder than the Sun, it radiates at much longer wavelengths, pri- common.
    [Show full text]
  • Keeling Curve: Result, Interpretation & Global Monitoring
    International Journal for Empirical Education and Research Keeling Curve: Result, Interpretation & Global Monitoring Augustyn Ostrowski Faculty of Geography & Geology Jagiellonian University Email: [email protected] (Author of Correspondence) Poland Abstract The Keeling Curve is a graph of the accumulation of carbon dioxide in the Earth's atmosphere based on continuous measurements taken at the Mauna Loa Observatory on the island of Hawaii from 1958 to the present day. The curve is named for the scientist Charles David Keeling, who started the monitoring program and supervised it until his death in 2005. Keywords: Mauna Loa Measurements; Results and Interpretation; Global Monitoring; Ralph Keeling. ISSN Online: 2616-4833 ISSN Print: 2616-4817 35 1. Introduction Keeling's measurements showed the first significant evidence of rapidly increasing carbon dioxide levels in the atmosphere. According to Dr Naomi Oreskes, Professor of History of Science at Harvard University, the Keeling curve is one of the most important scientific works of the 20th century. Many scientists credit the Keeling curve with first bringing the world's attention to the current increase of carbon dioxide in the atmosphere. Prior to the 1950s, measurements of atmospheric carbon dioxide concentrations had been taken on an ad hoc basis at a variety of locations. In 1938, engineer and amateur meteorologist Guy Stewart Callendar compared datasets of atmospheric carbon dioxide from Kew in 1898-1901, which averaged 274 parts per million by volume (ppm), and from the eastern United States in 1936-1938, which averaged 310 ppmv, and concluded that carbon dioxide concentrations were rising due to anthropogenic emissions. However, Callendar's findings were not widely accepted by the scientific community due to the patchy nature of the measurements.
    [Show full text]
  • How I Stave Off Despair As a Climate Scientist So Much Warming, So Many Dire Effects, So Little Action — Dave Reay Reveals YVONNE COOPER/UNIV
    WORLD VIEW A personal take on events How I stave off despair as a climate scientist So much warming, so many dire effects, so little action — Dave Reay reveals YVONNE COOPER/UNIV. EDINBURGH COOPER/UNIV. YVONNE how dreams of soggy soil and seaweed keep him going. here’s a curve that is quietly plotting our performance as a behind my eyelids, that’s what helps me sleep. species. This curve is not a commodity price or a technology That, and a personal plot to pull a lifetime’s worth of carbon out of index. It has no agenda or steering committee. It is the Keeling the atmosphere. Tcurve. It is painfully consistent in its trajectory and brutally honest in The dream with which I’ve bored my family to distraction for the its graphical indictment of our society as one that stands ready to stand past 20 years is going truly ‘net zero’: paring down emissions to the by as islands submerge, cities burn and coasts flood. bare minimum, and then managing a chunk of land to try to sequester Established by Charles David Keeling in 1958, the curve records the remainder. how much carbon dioxide is in our atmosphere — fewer than 330 parts Last month, that dream came true. Years of saving, a large dollop per million then, more than 400 today. Each month for the past decade, of luck and an even larger loan made me and my wife the nervous my geeky addiction has been to scan the latest data. To search for some owners of 28 hectares of rough grassland and wild rocky shores in hint that ‘Stabilization Day’ will come: when global emissions and the west of Scotland.
    [Show full text]
  • The Kelvin and Temperature Measurements
    Volume 106, Number 1, January–February 2001 Journal of Research of the National Institute of Standards and Technology [J. Res. Natl. Inst. Stand. Technol. 106, 105–149 (2001)] The Kelvin and Temperature Measurements Volume 106 Number 1 January–February 2001 B. W. Mangum, G. T. Furukawa, The International Temperature Scale of are available to the thermometry commu- K. G. Kreider, C. W. Meyer, D. C. 1990 (ITS-90) is defined from 0.65 K nity are described. Part II of the paper Ripple, G. F. Strouse, W. L. Tew, upwards to the highest temperature measur- describes the realization of temperature able by spectral radiation thermometry, above 1234.93 K for which the ITS-90 is M. R. Moldover, B. Carol Johnson, the radiation thermometry being based on defined in terms of the calibration of spec- H. W. Yoon, C. E. Gibson, and the Planck radiation law. When it was troradiometers using reference blackbody R. D. Saunders developed, the ITS-90 represented thermo- sources that are at the temperature of the dynamic temperatures as closely as pos- equilibrium liquid-solid phase transition National Institute of Standards and sible. Part I of this paper describes the real- of pure silver, gold, or copper. The realiza- Technology, ization of contact thermometry up to tion of temperature from absolute spec- 1234.93 K, the temperature range in which tral or total radiometry over the tempera- Gaithersburg, MD 20899-0001 the ITS-90 is defined in terms of calibra- ture range from about 60 K to 3000 K is [email protected] tion of thermometers at 15 fixed points and also described.
    [Show full text]
  • The Kibble Balance and the Kilogram
    C. R. Physique 20 (2019) 55–63 Contents lists available at ScienceDirect Comptes Rendus Physique www.sciencedirect.com The new International System of Units / Le nouveau Système international d’unités The Kibble balance and the kilogram La balance de Kibble et le kilogramme ∗ Stephan Schlamminger , Darine Haddad NIST, 100 Bureau Drive, Gaithersburg, MD 20899, USA a r t i c l e i n f o a b s t r a c t Article history: Dr. Bryan Kibble invented the watt balance in 1975 to improve the realization of the unit Available online 25 March 2019 for electrical current, the ampere. With the discovery of the Quantum Hall effect in 1980 by Dr. Klaus von Klitzing and in conjunction with the previously predicted Josephson effect, Keywords: this mechanical apparatus could be used to measure the Planck constant h. Following a Unit of mass proposal by Quinn, Mills, Williams, Taylor, and Mohr, the Kibble balance can be used to Kilogram Planck constant realize the unit of mass, the kilogram, by fixing the numerical value of Planck’s constant. Kibble balance In 2017, the watt balance was renamed to the Kibble balance to honor the inventor, who Revised SI passed in 2016. This article explains the Kibble balance, its role in the redefinition of the Josephson effect unit of mass, and attempts an outlook of the future. Quantum Hall effect Published by Elsevier Masson SAS on behalf of Académie des sciences. This is an open access article under the CC BY-NC-ND license Mots-clés : (http://creativecommons.org/licenses/by-nc-nd/4.0/).
    [Show full text]
  • Draft 9Th Edition of the SI Brochure
    —————————————————————————— Bureau International des Poids et Mesures The International System of Units (SI) 9th edition 2019 —————————————————— 2 ▪ Draft of the ninth SI Brochure, 5 February 2018 The BIPM and the Metre Convention The International Bureau of Weights and Measures (BIPM) was set up by the Metre As of 20 May 2019, fifty Convention signed in Paris on 20 May 1875 by seventeen States during the final session of nine States were Members of this Convention: the diplomatic Conference of the Metre. This Convention was amended in 1921. Argentina, Australia, 2 Austria, Belgium, Brazil, The BIPM has its headquarters near Paris, in the grounds (43 520 m ) of the Pavillon de Bulgaria, Canada, Chile, Breteuil (Parc de Saint-Cloud) placed at its disposal by the French Government; its upkeep China, Colombia, Croatia, is financed jointly by the Member States of the Metre Convention. Czech Republic, Denmark, Egypt, Finland, The task of the BIPM is to ensure worldwide unification of measurements; its function is France, Germany, Greece, Hungary, India, Indonesia, thus to: Iran (Islamic Rep. of), • establish fundamental standards and scales for the measurement of the principal physical Iraq, Ireland, Israel, Italy, Japan, Kazakhstan, quantities and maintain the international prototypes; Kenya, Korea (Republic • carry out comparisons of national and international standards; of), Lithuania, Malaysia, • ensure the coordination of corresponding measurement techniques; Mexico, Montenegro, Netherlands, New • carry out and coordinate measurements of the fundamental physical constants relevant Zealand, Norway, to these activities. Pakistan, Poland, Portugal, Romania, The BIPM operates under the exclusive supervision of the International Committee for Russian Federation, Saudi Weights and Measures (CIPM) which itself comes under the authority of the General Arabia, Serbia, Singapore, Slovakia, Slovenia, South Conference on Weights and Measures (CGPM) and reports to it on the work accomplished Africa, Spain, Sweden, by the BIPM.
    [Show full text]
  • A Rational Discussion of Climate Change: the Science, the Evidence, the Response
    A RATIONAL DISCUSSION OF CLIMATE CHANGE: THE SCIENCE, THE EVIDENCE, THE RESPONSE HEARING BEFORE THE SUBCOMMITTEE ON ENERGY AND ENVIRONMENT COMMITTEE ON SCIENCE AND TECHNOLOGY HOUSE OF REPRESENTATIVES ONE HUNDRED ELEVENTH CONGRESS SECOND SESSION NOVEMBER 17, 2010 Serial No. 111–114 Printed for the use of the Committee on Science and Technology ( Available via the World Wide Web: http://www.science.house.gov U.S. GOVERNMENT PRINTING OFFICE 62–618PDF WASHINGTON : 2010 For sale by the Superintendent of Documents, U.S. Government Printing Office Internet: bookstore.gpo.gov Phone: toll free (866) 512–1800; DC area (202) 512–1800 Fax: (202) 512–2104 Mail: Stop IDCC, Washington, DC 20402–0001 COMMITTEE ON SCIENCE AND TECHNOLOGY HON. BART GORDON, Tennessee, Chair JERRY F. COSTELLO, Illinois RALPH M. HALL, Texas EDDIE BERNICE JOHNSON, Texas F. JAMES SENSENBRENNER JR., LYNN C. WOOLSEY, California Wisconsin DAVID WU, Oregon LAMAR S. SMITH, Texas BRIAN BAIRD, Washington DANA ROHRABACHER, California BRAD MILLER, North Carolina ROSCOE G. BARTLETT, Maryland DANIEL LIPINSKI, Illinois VERNON J. EHLERS, Michigan GABRIELLE GIFFORDS, Arizona FRANK D. LUCAS, Oklahoma DONNA F. EDWARDS, Maryland JUDY BIGGERT, Illinois MARCIA L. FUDGE, Ohio W. TODD AKIN, Missouri BEN R. LUJA´ N, New Mexico RANDY NEUGEBAUER, Texas PAUL D. TONKO, New York BOB INGLIS, South Carolina STEVEN R. ROTHMAN, New Jersey MICHAEL T. MCCAUL, Texas JIM MATHESON, Utah MARIO DIAZ-BALART, Florida LINCOLN DAVIS, Tennessee BRIAN P. BILBRAY, California BEN CHANDLER, Kentucky ADRIAN SMITH, Nebraska RUSS CARNAHAN, Missouri PAUL C. BROUN, Georgia BARON P. HILL, Indiana PETE OLSON, Texas HARRY E. MITCHELL, Arizona CHARLES A. WILSON, Ohio KATHLEEN DAHLKEMPER, Pennsylvania ALAN GRAYSON, Florida SUZANNE M.
    [Show full text]
  • The International System of Units (SI)
    NAT'L INST. OF STAND & TECH NIST National Institute of Standards and Technology Technology Administration, U.S. Department of Commerce NIST Special Publication 330 2001 Edition The International System of Units (SI) 4. Barry N. Taylor, Editor r A o o L57 330 2oOI rhe National Institute of Standards and Technology was established in 1988 by Congress to "assist industry in the development of technology . needed to improve product quality, to modernize manufacturing processes, to ensure product reliability . and to facilitate rapid commercialization ... of products based on new scientific discoveries." NIST, originally founded as the National Bureau of Standards in 1901, works to strengthen U.S. industry's competitiveness; advance science and engineering; and improve public health, safety, and the environment. One of the agency's basic functions is to develop, maintain, and retain custody of the national standards of measurement, and provide the means and methods for comparing standards used in science, engineering, manufacturing, commerce, industry, and education with the standards adopted or recognized by the Federal Government. As an agency of the U.S. Commerce Department's Technology Administration, NIST conducts basic and applied research in the physical sciences and engineering, and develops measurement techniques, test methods, standards, and related services. The Institute does generic and precompetitive work on new and advanced technologies. NIST's research facilities are located at Gaithersburg, MD 20899, and at Boulder, CO 80303.
    [Show full text]
  • LECTURE #23: Mega Disasters – Climate Change
    GEOL 0820 Ramsey Natural Disasters Spring, 2021 LECTURE #23: Mega Disasters – Climate Change Date: 19 April 2021 I. Final Exam • same access as the mid-term exams using Canvas o I will send a reminder email to your Pitt email account over the weekend o the exam will “open” at the start of the assigned time period: Wednesday, April 28th at 2:00pm and close at 3:15pm • same format as the mid-term exams o except a little longer (~75 questions) nd o material: 2 half of hurricanes, flooding (plus the video), wildfires, mega- disasters o weeks 11 – 14 II. Early Earth • was more similar to present-day Venus than what we have today o very high amounts of carbon dioxide (CO2) in the atmosphere and MUCH hotter temperatures Venus early Earth Earth today carbon dioxide (CO2) 96.5% 98% 0.04% nitrogen (N2) 3.4% 1.9% 78% oxygen (O2) ~ 0% ~ 0% 21% argon (Ar) 0.007% 0.1% 0.93% average temperature (°F) 872 550 61 * average pressure (bars) 92 60 1 * Earth would be at/below 32° F with no CO2 (more like Mars is now)! o so, where did all the CO2 go? . 80% is in rocks like limestone (CaCO3) and other organic material (oil/gas/coal) Plate Tectonics! . some dissolved into the oceans . some is in living plants (plants converted CO2 and produced O2) . other biologic uses of CO2 (bones, shells) III. Long Term Climate Change • Earth’s history shows large variations in climate o from the very early Earth with its large CO2 percentages o to much later in history .
    [Show full text]
  • The Redefinition of the Ampere
    56TH INTERNATIONAL SCIENTIFIC COLLOQUIUM URN (Paper): urn:nbn:de:gbv:ilm1-2011iwk-151:3 Ilmenau University of Technology, 12 – 16 September 2011 URN: urn:nbn:gbv:ilm1-2011iwk:5 THE REDEFINITION OF THE AMPERE Franz Josef Ahlers, Uwe Siegner Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig ABSTRACT F/l = μ0·(I²/2πr) in vacuum. The numerical value of the magnetic constant μ0 is fixed through the -7 The ampere is one of the seven base units of the SI, definition of the ampere to μ0 = 4π·10 N/A² the international system of units. Its definition is Since the numerical value of the speed of light c linked to mechanical units, especially the unit of has been fixed through the definition of the meter, mass, the kilogram. In a future system of units, which also the numerical value of the electric constant ε0 is 2 will be based on the values of fundamental constants, fixed according to the Maxwell relation μ0·ε0·c = l. the ampere will be based on the value of the The practical implementation of this definition – elementary charge e. This paper describes the which, in metrology, is called realisation – must be technical background of the redefinition. performed with the aid of measuring arrangements that can be realised experimentally. One dis- Index Terms – SI units, Josephson effect, tinguishes between direct realisation – in which the quantum Hall effect, single electron effect current is related to a mechanical force – and indirect realisation. The latter is based on Ohm's law I = U/R and the ampere is realised through the realisation of 1.
    [Show full text]
  • This Is Nature; This Is Un-Nature: Reading the Keeling Curve
    Joshua P. Howe Downloaded from https://academic.oup.com/envhis/article-abstract/20/2/286/528915 by OUP site access user on 24 May 2019 This Is Nature; This Is Un-Nature: Reading the Keeling Curve Data images make odd cultural artifacts. On one hand, scientists pre- sent their data in images as a form of visual communication, intended, like other forms of visual culture, to convey both specific information and larger culturally coded messages. On the other hand, scientists typically hew to methods of measurement and math- ematical analysis intended to ensure that the data they present reflect some objective reality that transcends the cultural. To the extent that the data tell a cultural story, it is supposed to “speak for itself.” Such is the case with the Keeling Curve, the oscillating upward- sloping graph of measured atmospheric carbon dioxide (CO2) that has come to stand as one of the most important and powerful scien- tific symbols of anthropogenic climate change. To a lay reader, it may seem odd to read a simple measure of atmospheric gas through the many-sided prism of modern American life the way you might read a historical photograph or piece of art. And yet the Keeling Curve func- tions as much as a symbol in our collective cultural understanding of climate change as it does a representation of data about CO2. The Keeling Curve faithfully represents something quite real—the accumulation of CO2 in the atmosphere since 1958, expressed in parts per million (ppm)—but it is also a constructed image ripe for reading, similar to a painting, a photograph, a landscape, or a written document.
    [Show full text]