In a Washington Post Op-Ed, Alan Leshner hammers the nonsense from Sarah Palin:

Don’t be fooled about climate science. In April, 1994 — long after scientists had clearly demonstrated the addictive quality and devastating health impacts of cigarette smoking — seven chief executives of major tobacco companies denied the evidence, swearing under oath that nicotine was not addictive.

Now, the American public is again being subjected to those kinds of
denials, this time about global climate change. While former Alaska
governor Sarah Palin wrote in her Dec. 9 op-ed
that she did not deny the “reality of some changes in climate,” she
distorted the clear scientific evidence that Earth’s climate is
changing, largely as a result of human behaviors. She also badly
confused the concepts of daily weather changes and long-term climate
trends when she wrote that “while we recognize the occurrence of these
natural, cyclical environmental trends, we can’t say with assurance
that man’s activities cause weather changes.” Her statement
inaccurately suggests that short-term weather fluctuations must be
consistent with long-term climate patterns. And it is the long-term
patterns that are a cause for concern.

Climate-change science is clear: The concentration of atmospheric
carbon dioxide — derived mostly from the human activities of
fossil-fuel burning and deforestation — stands at 389 parts per
million (ppm). We know from studying ancient Antarctic ice cores that
this concentration is higher than it has been for at least the past
650,000 years. Exhaustive measurements tell us that atmospheric carbon
dioxide is rising by 2 ppm every year and that the global temperature
has increased by about 1.1 degrees Fahrenheit over the past century.
Multiple lines of other evidence, including reliable thermometer
readings since the 1880s, reveal a clear warming trend. The broader
impacts of climate change range from rapidly melting glaciers and
rising sea levels to shifts in species ranges.

via www.washingtonpost.com

Thousands of respected scientists at an array of institutions worldwide
agree that major health and economic impacts are likely unless we act
now to slow greenhouse gas emissions. Already, sea levels are estimated
to rise by 1 to 2 meters by the end of this century. Some scientists
have said that average temperatures could jump by as much as 4 degrees
Fahrenheit if the atmospheric carbon dioxide level reaches 450 ppm. We
may face even more dangerous impacts at 550 ppm, and above that level,
devastating events. U.S. crop productivity would be affected, while
European communities might suffer increased fatalities because of
intensely hot summers.

Doubters insist that the earth is not warming. This is in stark
contrast to the consensus of 18 of the world’s most respected
scientific organizations, who strongly stated in an Oct. 21 letter
to the U.S. Senate that human-induced climate change is real. Still,
the doubters try to leverage any remaining points of scientific
uncertainty about the details of warming trends to cast doubt on the
overall conclusions shared by traditionally cautious, decidedly
non-radical science organizations such as the National Academy of
Sciences and the American Association for the Advancement of Science,
which represents an estimated 10 million individual scientists through
262 affiliated societies. Doubters also make selective use of the
evidence, noting that the warming of the late 1990s did not persist
from 2001 to 2008, while ignoring the fact that the first decade of the
21st century looks like it will be the warmest decade on record.

None of these tactics changes the clear consensus of a vast majority
of scientists, who agree that the Earth is warming as greenhouse gas
levels rise. The public and policymakers should not be confused by a
few private e-mails that are being selectively publicized and, in any
case, remain irrelevant to the broad body of diverse evidence on
climate change. Selected language in the messages has been interpreted
by some to suggest unethical actions such as data manipulation or
suppression. To be sure, investigations are appropriate whenever
questions are raised regarding the transparency and rigor of the
scientific process or the integrity of individual scientists. We
applaud that the responsible authorities are conducting those
investigations. But it is wrong to suggest that apparently stolen
emails, deployed on the eve of the Copenhagen climate summit, somehow
refute a century of evidence based on thousands of studies.

Palin also errs by claiming that America can’t afford to reduce
greenhouse gases. The highly regarded Stern Commission revealed that
inaction could cost us
the equivalent of between 5 and 20 percent of global gross domestic
product per year. In contrast, the price of slowing emissions was
estimated to be 1 percent of GDP. China, meanwhile, reportedly is
investing heavily in clean energy technologies.

Now, policymakers must decide whether to act on the evidence or to
avoid facing one of the most crucial issues of our generation.

Alan I. Leshner is the chief executive officer of the American
Association for the Advancement of Science and executive publisher of
the journal Science.