Revised AGU Statement on Climate Change

The AGU has issued its revised statement on climate change, approved by the fifteen member committee chaired by Gerald North with one (predictable) dissent. 

Human induced climate change requires urgent action.

Humanity is the major influence on the global climate change observed over the past 50 years.

Rapid societal responses can significantly lessen negative outcomes.

Human activities are changing Earth’s climate. At the global level, atmospheric concentrations of carbon dioxide and other heat trapping greenhouse gases have increased sharply since the Industrial Revolution. Fossil fuel burning dominates this increase.  Human caused increases in greenhouse gases are responsible for most of the observed global average surface warming of roughly 0.8°C (1.5°F) over the past 140 years. Because natural processes cannot quickly remove some of these gases (notably carbon dioxide) from the atmosphere, our past, present, and future emissions will influence the climate
system for millennia. 

Extensive, independent observations confirm the reality of global warming. These observations show large scale increases in air and sea temperatures, sea level, and atmospheric water vapor; they document decreases in the extent of mountain glaciers, snow cover, permafrost, and Arctic sea ice. These changes are broadly consistent with long understood physics and predictions of how the climate system is expected to respond to human caused increases in greenhouse gases. The changes are inconsistent with explanations of climate change that rely on known natural influences.

Climate models predict that global temperatures will continue to rise, with the amount of warming primarily determined by the level of emissions. Higher emissions of greenhouse gases will lead to larger warming, and greater risks to society and ecosystems. Some additional warming is unavoidable due to past emissions.

Climate chan ge is not expected to be uniform over space or time. Deforestation, urbanization, and particulate pollution can have complex geographical, seasonal, and longer term effects on temperature, precipitation, and cloud properties. In addition, human induced climate change may alter atmospheric circulation, dislocating historical patterns of natural variability and storminess.

In the current climate, weather experienced at a given location or region varies from year to year; in a changing climate, both the nature of that variability and the basic patterns of weather experienced can change, sometimes in counterintuitive ways -- some areas may experience cooling, for instance. This raises no challenge to the reality of human induced climate change.

Impacts harmful to society, including increased extremes of heat, precipitation, and coastal high water are currently being experienced, and are projected to increase. Other projected outcomes involve threats to public health, water availability, agricultural productivity (particularly in low latitude developing countries), and coastal infrastructure, though some benefits may be seen at some times and places. Biodiversity loss is expected to accelerate due to both climate change and acidification of the oceans, which is a direct result of increasing carbon dioxide levels.

While important scientific uncertainties remain as to which particular impacts will be experienced where, no uncertainties are known that could make the impacts of climate change inconsequential. Furthermore, surprise outcomes, such as the unexpectedly rapid loss of Arctic summer sea ice, may entail even more dramatic changes than anticipated.

Actions that could diminish the threats posed by climate change to society and ecosystems include substantial emissions cuts to reduce the magnitude of climate change, as well as preparing for changes that are now unavoidable. The community of scientists has responsibilities to improve overall understanding of climate change and its impacts. Improvements will come from pursuing the research needed to understand climate change, working with stakeholders to identify relevant information, and conveying understanding clearly and accurately, both to decision makers and to the general public.

Adopted by the American Geophysical Union
December 2003; Revised and Reaffirmed December 2007, February 2012, August 2013.

The 15-person panel that reviewed and updated the position statement included the following:

• Amy Clement, Rosenstiel School of Marine and Atmospheric Science, University of Miami (approve)
• John Farrington, Woods Hole Oceanographic Institute (approve)
• Susan Joy Hassol, Climate Communication (approve)
• Robert Hirsch, U.S. Geological Survey (approve)
• Peter Huybers, Harvard University (approve)
• Peter Lemke, Alfred Wegener Institute (approve)
• Gerald North, Texas A&M University (approve, panel chair)
• Michael Oppenheimer, Princeton University (approve)
• Roger Pielke Sr., University of Colorado Boulder (dissent)
• Ben Santer, Lawrence Livermore National Laboratory (approve)
• Gavin Schmidt, Goddard Institute for Space Studies, NASA (approve)
• Leonard A. Smith, London School of Economics (approve)
• Eric Sundquist, U.S. Geological Survey (approve)
• Pieter Tans, National Oceanic and Atmospheric Administration (approve)

It is notable here that the committee was quite willing to vote the statement out based on a strong consensus but not unanimity. As Eli noted in December last after attending the Fall AGU meeting, climate scientists are not only 97% for the proposition that the climate is changing driven by human influences but that it is also dangerous.  Action to stop carbon emissions is needed immediately.

The mood of the attendees had shifted.  It was much sourer about the few in the atmospheric science community still running interference for inactivism.  People were being called out in private, but also in public and not just in sessions dealing with education and communication and blogging.

It is now clear to the climate science community that keeping your head down has not been an effective option for climate scientists for quite a while (see Kathryn Hayhoe).  The denialists and their funders are  coming for you in the Niemoeller sense, sooner or later.  This means that many in the community have woken up.  Those who do not, or believe they cannot, are feeling guilty about not supporting the science they are part of.  Those folks need to be encouraged and supported and come out.