New studies warn global warming risks higher than previously thought
February 24th, 2009 by Jim JustThe risk posed to mankind and the environment by even small changes in average global temperatures is much higher than believed just a short time ago. Even modest increases in GMT (global mean temperature) above 1990 levels could commit the climate system to the risk of very large impacts for many centuries due to large scale discontinuities such as the deglaciation of the Greenland ice sheets.
That’s the conclusion of a new study published by the Proceedings of the National Academy of Sciences updating a 2001 assessment by the Intergovernmental Panel on Climate Change (IPCC).
The researchers report:
Increases in drought, heat waves and floods are projected in many regions and would have adverse impacts, including increased water stress, wildfire frequency and flood risks starting at less than (1.8 degrees) of additional warming above 1990 levels.
Global temperatures have risen 0.22 degree since 1990.
The researchers also say that we’re already seeing effects of global warming:
It is now more likely than not that human activity has contributed to observed increases in heat waves, intense precipitation events, and the intensity of tropical cyclones.
MIT also warns that risks from global warming are much higher than previously believed. Its Joint Program on the Science and Policy of Climate Change issued a report in January titled “Probabilistic Forecast for 21st Century Climate Based on Uncertainties in Emissions (without Policy) and Climate Parameters.” The study reanalyzed their model’s 2003 projections using the latest data and concluded:
The MIT Integrated Global System Model is used to make probabilistic projections of climate change from 1861 to 2100. Since the model’s first projections were published in 2003 substantial improvements have been made to the model and improved estimates of the probability distributions of uncertain input parameters have become available. The new projections are considerably warmer than the 2003 projections, e.g., the median surface warming in 2091 to 2100 is 5.1°C compared to 2.4°C in the earlier study.
Their median projection for the atmospheric concentration of carbon dioxide in 2095 is 866 ppm, as shown in this graph conveniently posted by Joseph Romm at Climate Progress:
