In my Jan. 2 post, I brought up the issue of the evidentiary case for climate change and global warming, and how new scientific theories, particularly such far-reaching and profound ones, typically take decades, if not longer, to gain mainstream acceptance. While it appears that a majority of the lay public in the US intuitively finds reasons to agree with and accept it, whether or not global warming is taking place, and more particularly whether or not man-made carbon dioxide and greenhouse gas emissions are the primary agents accelerating the process, the issue is not yet settled within the scientific community.
It is clear from from U.S. Dept. of Energy data (see graph, Jan. 2 post), as well as that from other leading government and scientific organizations with access to our most accurate and extensive CO2 and greenhouse gas emissions data sets, that such emissions have increased dramatically since 1860. According to the best data available, the concentration of carbon dioxide in the atmosphere has increased by approximately 25% since the beginning of the industrial age, from about 280 parts per million to over 370 parts per million. The largest increases occurred in the last decades of the 20th century, with CO2 now accumulating at an annual 2 ppm rate.
The most plausible and likely reason for this appears to be the rapid increase in man-made, or anthropogenic, emissions related to industrial activity and transportation. Man-made increases in carbon dioxide and greenhouse gas emissions, along with changes in land use (clearing of forests for agriculture and development) stand out like a sore thumb as the most readily apparent large-scale change in carbon sources and sinks.
Climate science is relatively young and its methods and techniques new, however. Though evidence for accelerating global climate warming over this period has become sufficiently documented and explained to capture the attention and sway the opinion of political leaders and policy makers worldwide, whether or not anthropogenic greenhouse gas emissions is the cause has been even more hotly disputed.
A Warming Global Climate
NASA Goddard Institute for Space Studies researchers based at Columbia University in New York are at the forefront of the evolving field of climate science. Global warming has become more and more apparent since 1978, according to GISS research. The Earth has warmed another 0.5¬∞C since then, and warmed a total of 0.9¬∞C since 1880, according to GISS senior climate scientist James Hansen’s research.
The concern is that the level of atmospheric carbon dioxide is approaching, or may have even reached, a “tipping point” from which the effects of even slight increases are amplified by associated processes and from which there may be no possibility of reversing the trend – say the melting of the West Antarctic ice sheet, for instance. In a first ever of its kind, a NASA survey documented that Antarctica has lost much more ice to the sea than it gained from snowfall between 1992 and 2002.
“I think action [to reduce greenhouse gas emissions] is needed urgently, because we are on the precipice of a climate system ‘tipping point’,” Hansen was quoted as saying in a November 2007 NASA Earth Observatory article. “I believe the evidence shows with reasonable clarity that the level of additional global warming that would put us into dangerous territory is at most 1¬∞C.”
Ongoing increases in atmospheric CO2 and climate warming have myriad, costly and in cases devastating implications for people and societies around the world. On May 9 GISS announced the publication of new research that “suggests that greenhouse-gas warming may raise average summer temperatures in the eastern United States nearly 10 degrees Fahrenheit by the 2080s.”
Researchers analyzed nearly 30 years of observational temperature and precipitation data and used computer model simulations that considered soil, atmospheric, and oceanic conditions and projected changes in greenhouse gases to reach their conclusions.
The GISS weather prediction model used in the research is likely the first of its kind and is “advantageous because it assesses details about future climate at a smaller geographic scale than global models, providing reliable simulations not only on the amounts of summer precipitation, but also on its frequency and timing,” according to GISS. “This is an important capability for predicting summer temperatures because observed daily temperatures are usually higher on rainless days and when precipitation falls less frequently than normal.”
A Climatic Tipping Point?
Later that month, on May 30, research results from studies carried out by NASA and Columbia University Earth Institute found “that human-made greenhouse gases have brought the Earth’s climate close to critical tipping points, with potentially dangerous consequences for the planet.”
Using climate models, satellite data and paleoclimate records, the scientists concluded that “the West Antarctic ice sheet, Arctic ice cover, and regions providing fresh water sources and species habitat are under threat from continued global warming.” Their research was published in Atmospheric Chemistry and Physics.
The 0.6¬∞C increase in average global temperature in the past 30 years has been driven mainly by increasing greenhouse gases, the scientists found. “…only moderate additional climate forcing is likely to set in motion disintegration of the West Antarctic ice sheet and Arctic sea ice. Amplifying feedbacks include increased absorption of sunlight as melting exposes darker surfaces and speedup of iceberg discharge as the warming ocean melts ice shelves that otherwise inhibits ice flow.”
“If global emissions of carbon dioxide continue to rise at the rate of the past decade, this research shows that there will be disastrous effects, including increasingly rapid sea level rise, increased frequency of droughts and floods, and increased stress on wildlife and plants due to rapidly shifting climate zones,” lead author James Hansen concluded.
The authors concluded that additional global warming of about 1¬∞C (1.8¬∞F) or more above the global temperature in 2000 is likely to be dangerous. “The temperature limit implies that CO2 exceeding 450 ppm is almost surely dangerous, and the ceiling may be even lower,” co-author Makiko Sato of Columbia’s Earth Institute stated.