The Geological Society of America is proposing a formal position statement endorsing CO2 as the cause of global warming (Click to see Don Easterbrook PDF download
) and has invited members to comment. Attached are the comments which I have submitted to GSA.
FIRST........THE GEOLOGICAL SOCIETY OF AMERICA POSITION STATEMENT
The Geological Society of America concurs with key elements of recent assessments by the National Academies and the Intergovernmental Panel on Climate Change (IPCC). Global climate has warmed by ~0.7 °C since the middle to late 1800s, and human activities (mainly greenhouse-gas emissions) account for most of the warming since the middle 1900s. If current trends continue, the projected increase in global temperature by the end of the twenty-first century will result in large negative impacts on humans and other life forms. Addressing the challenges posed by future anthropogenic warming will require a combination of national and international emissions reductions and adaptations to those changes that occur.
This position statement (1) summarizes the recently strengthened basis for the conclusion that humans are the primary factor responsible for recent global warming; (2) describes the large effects on humans and ecosystems if greenhouse-gas concentrations and global climate reach projected levels; and (3) provides information for policy decisions guiding mitigation and adaptation strategies designed to address the future impacts of anthropogenic warming.
Recent scientific advances have eliminated or greatly reduced previous uncertainties about the size and causes of recent global warming. Ground-station measurements have shown a rapid warming trend of ~0.7 °C since the mid-1800s, and this trend is consistent with (1) retreat of northern hemisphere snow and Arctic sea ice in the last 40 years; (2) greater heat storage in the ocean over the last 50 years; (3) retreat of most mountain glaciers since 1850; (4) an ongoing rise of global sea level for more than a century; and (5) proxy reconstructions of temperature change over past centuries from ice cores, tree rings, and corals. Both instrumental records and proxy indices from geologic sources show a temperature rise since 1850 that is far more rapid than any in records extending back at least half a millennium.
Measurements from satellites beginning in 1979 initially did not show a warming trend, but later studies (Mears and Wentz, 2005; Santer et al., 2008) found that the satellite data had not been fully adjusted for losses of satellite elevation through time, differences in time of arrival over a given location, and removal of higher-elevation effects on the lower tropospheric signal. With these factors taken into account, the satellite data are now in basic agreement with ground-station data and confirm a warming trend since 1979. In a related study, Sherwood et al. (2005) found problems with corrections of tropical daytime radiosonde measurements and largely resolved a previous discrepancy with ground-station trends. As a result, the warming of Earth’s surface by ~0.7 °C since 1850 is no longer open to serious challenge.
Several potential causes of this warming trend can be eliminated. Long-term changes driven by changes in Earth’s orbit or its tectonism are far too slow to have played a significant role in a 150-year trend. Large volcanic eruptions cooled global climate for a year or two, and El Niño episodes warmed it for about a year, but neither factor dominates multi-decadal trends.
As a result, human influences and solar fluctuations are the only factors that could have changed rapidly enough and lasted long enough to explain the observed changes in global temperature. Although the 3rd (2001) IPCC report allowed that solar fluctuations might have contributed as much as 30% of the warming since 1850, subsequent observations of Sun-like stars (Foukal et al., 2004) and new simulations of the evolution of solar sources of irradiance variations (Wang et al., 2005) have reduced these estimates. The 4th IPCC report concluded that changes in solar irradiance, continuously measured by satellites since 1979, account for less than 10% of the recent warming.
Greenhouse gases remain as the major explanation. Climate model assessments of the natural and anthropogenic factors responsible for this warming conclude that rising anthropogenic emissions of greenhouse gases have been an important contributor since the mid-1800s and the major factor since the mid-1900s. The CO2 concentration in the atmosphere is now ~30% higher than peak levels measured in ice cores for the last 800,000 years, and the methane concentration is 2.5 times higher. Half of Earth’s warming has occurred through the basic heat-trapping effect of the gases in the absence of any feedback processes. This “clear-sky” part of the response to climate is known with high certainty. The other half of the estimated warming results from the net effect of feedbacks in the climate system: a very large positive feedback from water vapor; a smaller positive feedback from snow and ice albedo; and sizeable, but still uncertain, negative feedbacks from clouds and aerosols. The vertical structure of observed changes in temperature and water vapor in the troposphere is consistent with the anthropogenic greenhouse-gas “fingerprint” simulated by climate models (Santer et al., 2008). Considered in isolation, the greenhouse-gas increases during the last 150 years would have caused a warming larger than the one actually measured, but negative feedback from clouds and aerosols has offset part of the warming. In addition, because the oceans take decades to respond fully to climatic forcing, the climate system has yet to register the complete effect of gas increases in recent decades.
These advances in scientific understanding of recent warming form the basis for projections of future changes. If greenhouse-gas emissions follow the current trajectory beyond the twenty-first century, CO2 levels will reach two to four times pre-industrial levels, for a total warming of 2.4–4.6 °C compared to 1850. This range of changes would substantially alter the functioning of the planet in both positive and negative ways. Several negative changes involve risk to humans and other life forms: (1) continued shrinking of Arctic sea ice with effects on native cultures and ice-dependent biota; (2) less snow accumulation and earlier melt in mountains, with reductions in spring and summer runoff for agricultural and municipal water; (3) disappearance of mountain glaciers and their late-summer runoff; (4) increased evaporation from farmland soils and stress on crops; (5) greater soil erosion due to increases in heavy convective summer rainfall; (6) longer fire seasons and increases in fire frequency; (7) severe insect outbreaks in vulnerable forest stands; (8) acidification of the global ocean; and (9) fundamental changes in the composition, functioning, and biodiversity of many terrestrial and marine ecosystems. Melting of Greenland and West Antarctic ice (still highly uncertain as to amount), along with thermal expansion of seawater and melting of mountain glaciers, will cause substantial future sea-level rise along densely populated coastal regions, inundating farmland and dislocating people. Because Earth’s history shows past examples of large and abrupt changes occurring within decades, the possibility exists for rapid future changes in response to increased greenhouse-gas concentrations. Carbon-climate model simulations indicate that 10–20% of the anthropogenic CO2 “pulse” could stay in the atmosphere for thousands of years, extending the duration of fossil-fuel warming and its effects on humans and other life forms. The acidification of the global ocean, and its effect on ocean life, will last for tens of thousands of years.
Public Policy Aspects
Recent scientific investigations have strengthened the case for policy action to reduce greenhouse gas emissions and to adapt to unavoidable climate change. To strengthen the consensus for action, this statement from the Geological Society of America is intended to inform policymakers about improved knowledge of Earth’s climate systems based on recent advances in climate science. Geoscientific investigations have contributed to this improved understanding of the climate system and strengthened the case for human-caused global warming, providing policymakers with a unique perspective on which to base mitigation and adaptation strategies. Future climate change will pose societal, biological, economic, and strategic challenges that will require a combination of national and international emissions reductions and adaptations. These challenges will also require balanced and thoughtful national and international discussions leading to careful long-term planning and sustained policy actions.
• Public investment is needed to improve our understanding of how climate change impacts society, including on local and regional scales, and to formulate adaptation measures. Sustained support of climate-related research to advance understanding of the past and present operation of the climate system is needed, with particular focus on the major remaining uncertainties in understanding and predicting Earth’s future climate at regional and global scales. Focused research is needed to improve our ability to assess the response and resilience of natural and human systems to past, present, and future changes in the climate system.
• National and international planning is needed to address challenges posed by future climate change. Near-, mid-, and long-term strategies for climate-change evolution, adaptation, and mitigation, based in part on knowledge gained from studies of previous environmental changes, should be developed.
• Public policy should include effective strategies for the reduction of greenhouse-gas emissions. Earth has a virtually unlimited supply of low-carbon energy. Cost-effective investments to improve the efficiency of these natural resources can reduce the economic impacts of the needed changes.
Opportunities for GSA and GSA Members to Help Implement Recommendations
To facilitate implementation of the goals of this position statement, the Geological Society of America recommends that its members take the following actions:
• Actively participate in professional education and discussion activities so as to be technically well informed about the latest advances in climate science. GSA should encourage symposia at national and regional meetings to educate members on mainstream understanding among geoscientists and climate scientists of the causes and future effects of global warming within the broader context of natural variability. These symposia should seek to actively engage members in hosted discussions that clarify issues, possibly utilizing educational formats other than the traditional presentation and Q&A session.
• Engage in public education activities in the community, including at the local level. Public education is a critical element of a proactive response to the challenges presented by global climate change. GSA members are encouraged to take an active part in outreach activities to educate the public at all levels (local, regional, and national) about the science of global warming and the importance of geological research in framing policy development. Such activities can include organizing and participating in community school activities; leading discussion groups in churches or other civic organizations; meeting with local and state community leaders and congressional staffs; participating in GSA’s Congressional Visits Day; writing opinion pieces and letters to the editor for local and regional newspapers; contributing to online forums; and volunteering for organizations that support efforts to effectively mitigate and adapt to global climate change.
• Collaborate with a wide range of stakeholders to help educate and inform them about the causes and impacts of global climate change from the geosciences perspective.
GSA members are encouraged to discuss with businesses and policymakers the science of global warming, as well as the opportunities for transitioning from our predominant dependence on fossil fuels to greater use of low-carbon energies and energy efficiencies.
• Work interactively with other science and policy societies to help inform the public and ensure that policymakers have access to scientifically reliable information. GSA should actively engage and collaborate with other earth-science organizations in recommending and formulating national and international strategies to address impending impacts of anthropogenic climate change.
Foukal, P.G., et al., 2004, A stellar view on solar variations and climate: Science, v. 306, p. 68–69.
IPCC (Intergovernmental Panel on Climate Change), 2007, Summary for policymakers, in Climate Change 2007: The physical science basis: Cambridge, United Kingdom, Cambridge University Press, 18 p.
Mears, C.A., and Wentz, F.J., 2005, The effect of diurnal correction on satellite-derived lower tropospheric temperature: Science online, doi: 10.1126/science.1114772.
National Research Council, 2006, Surface temperature reconstructions for the last 2000 years: Washington, D.C., National Academy Press, 146 p.
Oerlemans, J., 2005, Extracting a climate signal from 169 glacier records: Science, v. 308, p. 675–677.
Santer, B., et al., 2008, Consistency of modeled and observed temperature trends in the tropical troposphere: International Journal of Climatology, v. 28, p. 1703–1722.
Sherwood, S., Lanzante, J., and Meyer, C., 2005, Radiosonde biases and late-20th century warming: Science online, doi: 10/1126/science.1115640.
Solomon, S., Plattner, G-K., Knutti, R., and Friedlingstein, P., 2009, Irreversible climate change due to carbon dioxide emissions: Proceedings of the National Academy of Sciences, v. 106, no. 6, p. 1704–1709.
Wang, Y.-M., Lean, J.L., and Sheeley, N.R., Jr., 2005, Modeling the Sun’s magnetic field and irradiance since 1713: Astrophysical Journal, v. 625, p. 522–538.
SELECTED WEB SITES
Intergovernmental Panel on Climate ChangeIPCC reports: www.ipcc.ch/
U.S. National AcademiesClimate Change at the National Academies: http://dels.nas.edu/climatechange/
Surface temperature reconstructions: http://www.nap.edu/catalog.php?record_id=11676#toc
U.S. Global Change Research ProgramHome page: http://www.globalchange.gov/
Satellite issue: http://www.climatescience.gov/Library/sap/sap1-1/finalreport/default.htm
Geologic record of abrupt changes: http://www.climatescience.gov/Library/sap/sap3-4/final-report/
Global climate change impacts in the United States: http://www.globalchange.gov/publications/reports/scientific-assessments/us-impacts
Click this PDF File to read A Response to Geological Society of America position statement by Don Easterbrook
See also Don J Easterbrook: Resume