Information about Climate Sensitivity
In Intergovernmental Panel on Climate Change (IPCC) reports, equilibrium climate sensitivity refers to the equilibrium change in global mean surface temperature following a doubling of the atmospheric (equivalent) CO2 concentration. This value is estimated, by the IPCC Fourth Assessment Report as likely to be in the range 2 to 4.5°C with a best estimate of about 3°C, and is very unlikely to be less than 1.5°C. Values substantially higher than 4.5°C cannot be excluded, but agreement of models with observations is not as good for those values. This is a slight change from the IPCC Third Assessment Report, which said it was "likely to be in the range of 1.5 to 4.5°C" [1]. More generally, equilibrium climate sensitivity refers to the equilibrium change in surface air temperature following a unit change in radiative forcing, expressed in units of °C/(W/m2). In practice, the evaluation of the equilibrium climate sensitivity from models requires very long simulations with coupled global climate models, or it may be deduced from observations.
Gregory et al. (2002) estimate a lower bound of 1.6°C by estimating the change in Earth's radiation budget and comparing it to the global warming observed over the 20th century. Recent work by Annan and Hargreaves [2] combines independent observational and model based estimates to produce a mean of about 3°C, and only a 5% chance of exceeding 4.5°C. A general discussion of some recent work is given here.
Shaviv (2005) carried out a similar analysis for 6 different time scales, ranging from the 11-yr solar cycle to the climate variations over geological time scales. He found a typical sensitivity of 2.0°C (ranging between 0.9°C and 2.9°C at 99% confidence) if there is no cosmic-ray climate connection, or a typical sensitivity of 1.3°C (between 0.9°C and 2.5°C at 99% confidence), if the cosmic-ray climate link is real. More on climate sensitivity and this work can be found here.
Andronova and Schlesinger (2001) (using simple climate models) found that it could lie between 1 and 10°C, with a 54 percent likelihood that the climate sensitivity lies outside the IPCC range [3]. The exact range depends on which factors are most important during the instrumental period: "At present, the most likely scenario is one that includes anthropogenic sulfate aerosol forcing but not solar variation. Although the value of the climate sensitivity in that case is most uncertain, there is a 70 percent chance that it exceeds the maximum IPCC value. This is not good news." said Schlesinger.
Forest et al. (2002) using patterns of change and the MIT EMIC estimated a 95% confidence interval of 1.4–7.7°C for the climate sensitivity, and a 30% probability that sensitivity was outside the 1.5 to 4.5°C range.
Frame et al. (2005) and Allen et al. note that the size of the confidence limits are dependent on the nature of the prior assumptions made.
Climate sensitivity is not the same as the expected climate change at, say 2100: the TAR reports this to be an increase of 1.4 to 5.8°C over 1990.
The Transient climate response (TCR) - a term first used in the TAR - is the temperature change at the time of CO2 doubling in a run with CO2 increasing at 1%/year.
The effective climate sensitivity is a related measure that circumvents this requirement. It is evaluated from model output for evolving non-equilibrium conditions. It is a measure of the strengths of the feedbacks at a particular time and may vary with forcing history and climate state. Details are discussed in Section 9.2.1 of Chapter 9 in the TAR [4].
The Geologic temperature record are changes in Earth's environment as determined from geologic evidence on multi-million to billion (109) year time scales.
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Gregory et al. (2002) estimate a lower bound of 1.6°C by estimating the change in Earth's radiation budget and comparing it to the global warming observed over the 20th century. Recent work by Annan and Hargreaves [2] combines independent observational and model based estimates to produce a mean of about 3°C, and only a 5% chance of exceeding 4.5°C. A general discussion of some recent work is given here.
Shaviv (2005) carried out a similar analysis for 6 different time scales, ranging from the 11-yr solar cycle to the climate variations over geological time scales. He found a typical sensitivity of 2.0°C (ranging between 0.9°C and 2.9°C at 99% confidence) if there is no cosmic-ray climate connection, or a typical sensitivity of 1.3°C (between 0.9°C and 2.5°C at 99% confidence), if the cosmic-ray climate link is real. More on climate sensitivity and this work can be found here.
Andronova and Schlesinger (2001) (using simple climate models) found that it could lie between 1 and 10°C, with a 54 percent likelihood that the climate sensitivity lies outside the IPCC range [3]. The exact range depends on which factors are most important during the instrumental period: "At present, the most likely scenario is one that includes anthropogenic sulfate aerosol forcing but not solar variation. Although the value of the climate sensitivity in that case is most uncertain, there is a 70 percent chance that it exceeds the maximum IPCC value. This is not good news." said Schlesinger.
Forest et al. (2002) using patterns of change and the MIT EMIC estimated a 95% confidence interval of 1.4–7.7°C for the climate sensitivity, and a 30% probability that sensitivity was outside the 1.5 to 4.5°C range.
Frame et al. (2005) and Allen et al. note that the size of the confidence limits are dependent on the nature of the prior assumptions made.
Climate sensitivity is not the same as the expected climate change at, say 2100: the TAR reports this to be an increase of 1.4 to 5.8°C over 1990.
The Transient climate response (TCR) - a term first used in the TAR - is the temperature change at the time of CO2 doubling in a run with CO2 increasing at 1%/year.
The effective climate sensitivity is a related measure that circumvents this requirement. It is evaluated from model output for evolving non-equilibrium conditions. It is a measure of the strengths of the feedbacks at a particular time and may vary with forcing history and climate state. Details are discussed in Section 9.2.1 of Chapter 9 in the TAR [4].
References
- Andronova, N., and M. E. Schlesinger. 2001. Objective Estimation of the Probability Distribution for Climate Sensitivity. J. Geophys. Res. 106, D19, 22605. http://crga.atmos.uiuc.edu/publications/Objective_Est_dT2x.pdf data: http://crga.atmos.uiuc.edu/publications/Climate.html
- Annan, J.D., and J. C.Hargreaves, 2006. Using multiple observationally-based constraints to estimate climate sensitivity. Geophysical Research Letters 33, L06704, 2006 http://dx.doi.org/10.1029/2005GL025259 (preprint)
- Forest, C.E., P.H. Stone, A.P. Sokolov, M.R. Allen, and M.D. Webster, 2002. Quantifying uncertainties in climate system properties with the use of recent observations. Science, 295. 24 ([https://dspace.mit.edu/bitstream/1721.1/3567/1/MITJPSPGC_Rpt78.pdf preprint])
- Frame, D.J., B.B.B. Booth, J.A. Kettleborough, D.A. Stainforth, J.M. Gregory, M. Collins, and M.R. Allen, 2005. Constraining climate forecasts: the role of prior assumptions. Geophysical Research Letters, 32, L09702, doi:10.1029/2004GL022241. http://www.agu.org/pubs/crossref/2005/2004GL022241.shtml
- Gregory J.M., R.J. Stouffer, S.C.B. Raper, P.A. Stott, and N.A. Rayner, 2002. "An observationally based estimate of the climate sensitivity''. Journal of Climate, 15, 3117. http://ams.allenpress.com/perlserv/?request=get-abstract&issn=1520-0442&volume=015&issue=22&page=3117
- Shaviv, N.J., 2005. On climate response to changes in the cosmic ray flux and radiative budget. J. Geophys. Res. 110, A08105. http://www.agu.org/pubs/crossref/2005/2004JA010866.shtml (preprint)
Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), to evaluate the risk of climate change caused by human activity.
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Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state.
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Climate Change 2007, the Fourth Assessment Report (AR4) of the United Nations Intergovernmental Panel on Climate Change (IPCC), is the fourth in a series of such reports.
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The IPCC Third Assessment Report is an assessment of available scientific and socio-economic information on climate change by an intergovermental panel (IPCC) established by the United Nations Environment Programme (UNEP) and the UN's World Meteorological Organization (WMO).
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In climate science, radiative forcing is (loosely) defined as the difference between the incoming radiation energy and the outgoing radiation energy in a given climate system.
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General Circulation Models (GCMs) are a class of computer-driven models for weather forecasting, understanding climate and projecting climate change, where they are commonly called Global Climate Models.
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Solar variations are changes in the amount of radiant energy emitted by our Sun. There are periodic components to these variations, the principal one being the 11-year solar cycle (or sunspot cycle), as well as fluctuations which are aperiodic.
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The IPCC Third Assessment Report is an assessment of available scientific and socio-economic information on climate change by an intergovermental panel (IPCC) established by the United Nations Environment Programme (UNEP) and the UN's World Meteorological Organization (WMO).
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Global warming refers to the increase in the average temperature of the Earth's near-surface air and oceans in recent decades and its projected continuation.
The global average air temperature near the Earth's surface rose 0.74 ± 0.18 °C (1.33 ± 0.
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The global average air temperature near the Earth's surface rose 0.74 ± 0.18 °C (1.33 ± 0.
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Climate change refers to the variation in the Earth's global climate or in regional climates over time. It describes changes in the variability or average state of the atmosphere over time scales ranging from decades to millions of years.
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temperature record shows the fluctuations of the temperature of the atmosphere and the oceans through various spans of time. The most detailed information exists since 1850, when methodical thermometer-based records began.
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instrumental temperature record shows the fluctuations of the temperature of the atmosphere and the oceans as measured by temperature sensors. A quasi-global record exists since about 1850.
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Satellite temperature measurements have been obtained for troposphere since 1978. By comparison, the usable balloon (radiosonde) record begins in 1958.
Satellites do not measure "temperature" as such.
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Satellites do not measure "temperature" as such.
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temperature record of the past 1000 years describes the reconstruction of temperature for the last 1000 years on the Northern Hemisphere. A reconstruction is needed because a reliable surface temperature record exists only since about 1850.
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Warmest years on record
2005 0.6061
2002 0.5574
2006 0.5422
2001 0.4906
1999 0.3938
1990 0.3641
1991 0.3206
1988 0.3047
1994 0.2758
1996 0.2562
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2005 0.6061
2002 0.5574
2006 0.5422
2001 0.4906
1999 0.3938
1990 0.3641
1991 0.3206
1988 0.3047
1994 0.2758
1996 0.2562
References
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For temperature changes on other time scales, see .
The Geologic temperature record are changes in Earth's environment as determined from geologic evidence on multi-million to billion (109) year time scales.
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Attribution of recent climate change is the effort to scientifically ascertain mechanisms responsible for relatively recent changes observed in the Earth's climate. The effort has focused on changes observed during the period of instrumental temperature record, when records are
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National and international science academies and professional societies have assessed the current scientific opinion on climate change, in particular recent global warming.
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Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state.
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Deforestation is the conversion of forested areas to non-forest land for use such as arable land, pasture, urban use, logged area, or wasteland.[] Generally, the removal or destruction of significant areas of forest cover has resulted in a degraded environment with
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Global dimming is the gradual reduction in the amount of global direct irradiance at the Earth's surface that was observed for several decades after the start of systematic measurements in 1950s.
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Global warming potential (GWP) is a measure of how much a given mass of greenhouse gas is estimated to contribute to global warming. It is a relative scale which compares the gas in question to that of the same mass of carbon dioxide (whose GWP is by definition 1).
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greenhouse effect is the process in which the emission of infrared radiation by the atmosphere warms a planet's surface. The name comes from an incorrect analogy with the warming of air inside a greenhouse compared to the air outside the greenhouse.
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Greenhouse gases are components of the atmosphere that contribute to the greenhouse effect. Without the greenhouse effect the Earth would be uninhabitable;[1] in its absence, the mean temperature of the earth would be about -19 °C (-2 °F, 254 K) rather than the present
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Keeling curve is a graph showing the variation in concentration of atmospheric carbon dioxide since 1958. It shows that some factors (possibly human activities) are increasing the greenhouse effect with implications for global warming.
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urban heat island (UHI) is a metropolitan area which is significantly warmer than its surroundings. The temperature difference usually is larger at night than during the day and larger in winter than in summer, and is most apparent when winds are weak.
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Cloud forcing (sometimes described as 'cloud radiative forcing') is the difference between the radiation budget components for average cloud conditions and cloud-free conditions.
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glacier is a large, slow moving river of ice, formed from compacted layers of snow, that slowly deforms and flows in response to gravity. Glacier ice is the largest reservoir of fresh water on Earth, and second only to oceans as the largest reservoir of total water.
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Global cooling in general can refer to a cooling of the Earth. More specifically, it refers to a conjecture during the 1970s of imminent cooling of the Earth's surface and atmosphere along with a posited commencement of glaciation.
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Milankovitch cycles are the collective effect of changes in the Earth's movements upon its climate, named after Serbian civil engineer and mathematician Milutin Milanković.
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Herod_Archelaus
