By David L. Brown
It’s official. Global warming is real and human activity is a significant cause. That word comes today from the official scientific advisory agency of the United States government.
In a report prepared at the request of Congress, a committee of the National Research Council has concluded that the Earth is warmer today than it has been for at least the last 400 years, and quite likely for thousands of years. Chartered by Congress, the Council is part of the National Academies of Sciences.
According to a news release issued by the Academies today:
The committee pointed out that surface temperature reconstructions for periods before the Industrial Revolution — when levels of atmospheric greenhouse gases were much lower — are only one of multiple lines of evidence supporting the conclusion that current warming is occurring in response to human activities, and they are not the primary evidence.
The new report was requested to address controversy surrounding a study published by climate scientists Michael Mann, Raymond Bradley and Malcolm Hughes which concluded that the globe was the warmest for at least 1000 years, that the 1990’s was the warmest decade, and that 1998 was the warmest year on record. [Ed. note: Today 2005 is recognized as the warmest year.] Their graph showing a steep rise in temperatures after a long period of stability became known as the “hockey stick.”
Today’s news release said the committee study judged “the Mann team’s conclusion that warming in the last few decades of the 20th century was unprecedented over the last thousand years to be plausible,” adding that evidence is certain only for years since 1600. But the report stated that “recent warmth is unprecedented for at least the last 400 years and potentially the last several millennia.”
According to an Associated Press, “the report was requested in November by the chairman of the House Science Committee, Rep. Sherwood Boehlert, R-N.Y., to address naysayers who question whether global warming is a major threat.”
According to the AP story, Boehlert said “there is nothing in this report that should raise any doubts about the broad scientific consensus on global climate change.”
The findings of Mann and his associates had been attacked by poliicians and industry spokespersons who deny that global warming is real, and that human activity is a cause. For several years the broad general consensus among scientists has been that global warming is a demonstrated phenomenon.
Divisive arguments on this issue have had the unfortunate result of delaying action that might help mitigate the potentially devastating effects of climate change. Let us hope that this clear message from the National Academies will help end the pointless squabbling and create the resolve needed to begin seeking solutions.