Antarctica cooling controversy

Antarctica cooling controversy

The Antarctica cooling controversy relates to questions posed in popular media regarding whether or not current temperature trends in Antarctica cast doubt on global warming. Observations unambiguously show the Antarctic Peninsula to be warming. Trends elsewhere on the continent show both warming and cooling but are smaller and dependent on season and the timespan over which the trend is computed. [ [ Monthly mean surface temperature data and derived statistics for some Antarctic stations] from ""] Climate models predict that temperature trends due to global warming will be much smaller in Antarctica than in the Arctic, [ [ IPCC Working Group I] ] mainly because heat uptake by the Southern Ocean acts to moderate the radiative forcing by greenhouse gases. The depletion of stratospheric ozone also has had a cooling effect, since ozone acts as a greenhouse gas.

There is no similar controversy within the scientific community, as the small observed changes in Antarctica are consistent with the small changes predicted by climate models. Various global warming skeptics, most notably novelist Michael Crichton,Cite web| url= | author=Michael Crichton |title=The Case for Skepticism in Global Warming |publisher=Michael Crichton The official site | date=2005-01-25 | accessdate=2008-08-14 | language= Speech at the National Press Club, Washington, D.C.] have asserted that the Antarctic data contradict global warming. The few scientists who have commented on the supposed controversy state that there is no contradiction, [ [ Antarctic cooling, global warming?] Real Climate December 2004] while the author of the paper whose work inspired Crichton's remarks has said that Crichton "misused" his results.Cite news| url= | author=Peter Doran |title=Cold, Hard Facts |publisher=The New York Times | date=2006-07-27 | accessdate=2008-08-14 | language= ]

Observations of trends

Antarctica has few long-term records. There are less than twenty stations in all and only two in the interior. Hence calculation of a trend for the entire continent is difficult. Satellite observations only exist since 1981 and provide surface temperature measurements only in cloud-free conditions.

The 2007 IPCC Fourth Assessment Report states that "Observational studies have presented evidence of pronounced warming over the Antarctic Peninsula, but little change over the rest of the continent during the last half of the 20th century". [cite web|title=Regional Climate Projections (In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change)|author=J.H. Christensen, B. Hewitson, A. Busuioc, A. Chen, X. Gao, I. Held, R. Jones, R.K. Kolli, W.-T. Kwon, R. Laprise, V. Magaña Rueda, L. Mearns, C.G. Menéndez, J. Räisänen, A. Rinke, A. Sarr, P. Whetton|url=|year=2007|format=PDF|accessdate=2007-11-05] Chapman and Walshcite journal|title=A Synthesis of Antarctic Temperatures|author=William L. Chapman and John E. Walsh|journal=Journal of Climate|volume=20|issue=16|pages=4096–4117|url=|year=2007|accessdate=2007-11-05|doi=10.1175/JCLI4236.1] [cite web |url= |title=A synthesis of Antarctic temperatures |author=William L. Chapman and John E. Walsh |publisher=Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign |date=2005 |accessdate=2008-08-14 |language= ] note that "Trends calculated for the 1958–2002 period suggest modest warming over much of the 60°–90°S domain. All seasons show warming, with winter trends being the largest at +0.172 °C per decade while summer warming rates are only +0.045 °C per decade. The 45-yr temperature trend for the annual means is +0.082 °C per decade corresponding to a +0.371 °C temperature change over the 1958–2002 period of record. Trends computed using these analyses show considerable sensitivity to start and end dates, with trends calculated using start dates prior to 1965 showing overall warming, while those using start dates from 1966 to 1982 show net cooling over the region." Several scientific sourcescite journal|url= |title=Variability and Trends in Antarctic Surface Temperatures from In Situ and Satellite Infrared Measurements |author=Josefino C. Comiso |journal=Journal of Climate |volume=13 |issue=10 |pages=1674–1696|year=2000 |doi=10.1175/1520-0442(2000)013 |accessdate=2008-08-14 |language= PDF available at AMS Online] cite journal |url= |title=Interpretation of Recent Southern Hemisphere Climate Change |author=David W. J. Thompson and Susan Solomon |journal=Science|volume=296 |issue=5569 |pages=895-899|year=2002 |doi=10.1126/science.1069270 |accessdate=2008-08-14 |language= PDF availabe at Annular Modes Website] have reported that there is a cooling trend observed in the interior of the continent for the last two decades of the 20th century, while the Antarctic Peninsula shows a warming trend.

Doran et al. (2002)cite journal |url= |title=Antarctic climate cooling and terrestrial ecosystem response |author=Doran et al. |journal=Nature |volume=415 |issue=6871 |pages=517-520|year=2002 |doi=10.1038/nature710 |accessdate=2008-08-14 |language= in Letters to Nature 2002-01-13] [Cite web| url= | author=Doran et al. |title=Antarctic climate cooling and terrestrial ecosystem response|publisher=University of Illinois at Chicago | date=2002-01-13 | accessdate=2008-08-14 |language= PDF version: advance online publication Letters to Science] find that "Although previous reports suggest slight recent continental warming our spatial analysis of Antarctic meteorological data demonstrates a net cooling on the Antarctic continent between 1966 and 2000, particularly during summer and autumn. The McMurdo Dry Valleys have cooled by 0.7 °C per decade between 1986 and 2000, with similar pronounced seasonal trends... Continental Antarctic cooling, especially the seasonality of cooling, poses challenges to models of climate and ecosystem change".

There has been a public dispute regarding the apparent contradiction in the observed behavior of Antarctica, as opposed to the global rise in temperatures measured elsewhere in the world. This became part of the debate in the global warming controversy, particularly between advocacy groups of both sides in the public arena [ [ Antarctic Cooling Down; The Antarctic Ice Sheet is Growing; Hansen Downgrades Warming Threat | cooler heads ] ] [ [ CO2 Science ] ] [ [ Guess what? Antarctica's getting colder, not warmer | ] ] [ [ Media Matters - Beck's global warming special dominated by industry-funded "experts," serial misinformers ] ] , including politicians [ [ U.S. Senate Committee on Environment and Public Works ] ] , as well as the popular media. [ [ Media goofed on Antarctic data / Global warming interpretation irks scientists ] ] [ [ Ozone Hole Is Now Seen as a Cause for Antarctic Cooling - New York Times ] ] [ [ Antarctica Gives Mixed Signals on Warming ] ] [ [ - Antarctic cooling pushing life closer to the edge ] ] [ [ Antarctic cools in warmer world - Telegraph ] ] [ [ - Scientific winds blow hot and cold in Antarctica - January 25, 2002 ] ] [ [ The Melting (Freezing) of Antarctica; Deciphering Contradictory Climate Patterns Is Largely a Matter of Ice - New York Times ] ] [ [ Antarctic Ice Collapse Began End of Ice Age? ] ] In contrast to the popular press, there is no evidence of a corresponding "controversy" in the scientific community.

Origin of the "controversy"

Some public commentators have argued that this possible cooling trend observed in the interior of the Antarctica shows the lack of reliability of the models used for global warming predictions and even of climate theory in general. These arguments are made despite the fact that the small and variable observed trends are broadly consistent with the small magnitude of model-predicted temperature trends for Antarctica. The argument was popularized in Michael Crichton's 2004 fiction novel State of Fear. This novel has a docudrama plot based upon the idea that there is a deliberately alarmist conspiracy behind global warming activism. The author advocates skepticism in this matter. [Cite web| url= | author=Michael Crichton |title=Testimony before the United States Senate |publisher=Michael Crichton The official site | date=2005-09-28 | accessdate=2008-08-14 | language= Testimony before the Committee on Environment and Public Works, Washington, D.C.]

As presented in page 193 of "State of Fear": "The data show that one relatively small area called the Antarctic Peninsula is melting and calving huge icebergs. That's what gets reported year after year. But the continent as a whole is getting colder, and the ice is getting thicker". [Citation | last = Crichton | first = Michael | year = 2004 | title = State of Fear| publisher = HarperCollins, New York| id = ISBN 0-06-621413-0| pages = 109|language= First Edition] Crichton's footnote source is Doran et al., 2002.

A rebuttal to Crichton's claims was presented by the group Real Climate:Cite web| url= | author= Eric Steig and Gavin Schmidt |title=Antarctic cooling, global warming? |publisher=Real Climate | date=2004-12-03 | accessdate=2008-08-14 | language= ]

:"Long term temperature data from the Southern Hemisphere are hard to find, and by the time you get to the Antarctic continent, the data are extremely sparse. Nonetheless, some patterns do emerge from the limited data available. The Antarctic Peninsula, site of the now-defunct Larsen-B ice shelf, has warmed substantially. On the other hand, the few stations on the continent and in the interior appear to have cooled slightly (Doran et al, 2002; GISTEMP)"."

:"At first glance this seems to contradict the idea of “global” warming, but one needs to be careful before jumping to this conclusion. "A rise in the global mean temperature does not imply universal warming. Dynamical effects (changes in the winds and ocean circulation) can have just as large an impact, locally as the radiative forcing from greenhouse gases. The temperature change in any particular region will in fact be a combination of radiation-related changes (through greenhouse gases, aerosols, ozone and the like) and dynamical effects. Since the winds tend to only move heat from one place to another, their impact will tend to cancel out in the global mean"."

The leading author of the research paper, Peter Doran, published a statement in the New York Times stating that "... "our results have been misused as “evidence” against global warming by Michael Crichton in his novel “State of Fear"”... "Our study did find that 58 percent of Antarctica cooled from 1966 to 2000. But during that period, the rest of the continent was warming. And climate models created since our paper was published have suggested a link between the lack of significant warming in Antarctica and the ozone hole over that continent. These models, conspicuously missing from the warming-skeptic literature, suggest that as the ozone hole heals — thanks to worldwide bans on ozone-destroying chemicals — all of Antarctica is likely to warm with the rest of the planet. An inconvenient truth"?" He also emphasized the need for more stations in the Antarctic continent in order to obtain more robust results.

It is common to find statements that "climate models generally predict amplified warming in polar regions", e.g. Doran et al. In fact, climate models predict amplified warming only for the Arctic and not for Antarctica.

cientific sources and interpretations

According to a NASA press release: [Cite web| url= | author=NASA |title=Antarctic Temperature Trend 1982-2004 |publisher=Earth Observatory Newsroom | date= 2004| accessdate=2008-08-14 | language= NASA image based on data provided by Josefino Comiso, NASA-GSFC] :"Across most of the continent and the surrounding Southern Ocean, temperatures climbed... The temperature increases were greater and more widespread in West Antarctica than in East Antarctica, where some areas showed little change or even a cooling trend. This variability in temperature patterns across Antarctica complicates the work of scientists who are trying to understand the relative influence of natural cycles and human-caused climate change in Antarctica"."

As a complement to NASA's findings, the British Antarctic Survey, which has undertaken the majority of Britain's scientific research in the area, has the following positions: [ [ Climate Change - Our Research - British Antarctic Survey ] ]

* Ice makes polar climate sensitive by introducing a strong positive feedback loop.
* Melting of continental Antarctic ice could contribute to global sea level rise.
* Climate models predict more snowfall than ice melting during the next 50 years, but models are not good enough for them to be confident about the prediction.
* Antarctica seems to be both warming around the edges and cooling at the center at the same time. Thus it is not possible to say whether it is warming or cooling overall.
* There is no evidence for a decline in overall Antarctic sea ice extent.
* The central and southern parts of the west coast of the Antarctic Peninsula have warmed by nearly 3 °C. The cause is not known.
* Changes have occurred in the upper atmosphere over Antarctica.

Research by Thompson and Solomon (2002) and by Shindell and Schmidt (2004) [ [ Southern Hemisphere climate response to ozone changes and greenhouse gas increases ] ] [ [ GEOPHYSICAL RESEARCH LETTERS, VOL. 31, 2004 - Drew T. Shindell and Gavin A. Schmidt "Southern Hemisphere climate response to ozone changes and greenhouse gas increases" Full PDF] ] provide explanations for the observed cooling trend.


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