ONE TOWN SQUARE: at the intersection of peak oil, climate change, and land use

Today marks the release of the ‘meteorological year’ (December – November) averages for the surface temperature records (GISTEMP, HadCRU, NCDC).

RealClimate advises looking at 5-year averages, as this cuts through the “noise” in the annual numbers. What do we see?

More robustly, the most recent 5-year averages are all significantly higher than any in the last century. The last decade is by far the warmest decade globally in the record.

NOAA has posted a summary of 2008 highlights. NCDC, using a calendar year, ranks 2008 as ninth warmest if expected trends continue through December. A similar NASA analysis indicates that the January – November global temperature was 0.76 degree F (0.42 degree C) above the 20th century mean.

NOAA reports that the global land surface temperature for 2008 was the fifth warmest on record, with an average temperature 1.44 degrees F (0.80 degree C) above the 20th century mean of 48.1 degrees F (9.0 degrees C). Looking at the land data alone filters out the cooling impact of the La Niña that impacted the Pacific in the first half of the year.

Arctic sea ice extent in 2008 reached its second lowest melt season extent on record.

The 2008 Atlantic hurricane season was the third most costly on record in current dollars, after 2005 and 2004, and the fourth most active year since 1944.

The United States Geological Survey has published a new report titled Abrupt Climate Change. Peter Clark and Edward Brook, both of whom are in the Department of Geosciences at Oregon State University, were contributors to the report.

Chapter 2, “Rapid Changes in Glaciers and Ice Sheets and their Impacts on Sea Level,” observes that our current models can’t predict the changes in ice sheets and glaciers that we’re already seeing. The report reviews the new data accumulating about ice flow processes and concludes that “Inclusion of these processes in models will likely lead to sea-level projections for the end of the 21st century that substantially exceed the projections presented in the IPCC AR4 report (0.28 ± 0.10 m to 0.42 ± 0.16 m rise).”

During the last interglacial period (~120 thousand years ago) with similar carbon dioxide levels to pre-industrial values and Arctic summer temperatures up to 4° C warmer than today, sea level was 4-6 meters above present. The report points out the obvious: with sufficient time at elevated atmospheric CO2 levels, sea levels will continue to rise to historic levels as ice sheets continue to lose mass.

Joseph Romm at Climate Progress point out that the recent post-IPCC literature has been quite consistent in warning of sea level rise of one meter or more by 2100. There’s a 2008 Science study  (“Startling new sea level rise research: “Most likely” 0.8 to 2.0 meters by 2100”), a 2007 Science article (A Semi-Empirical Approach to Projecting Future Sea-Level Rise) projecting that sea levels could be up to 5 feet higher in 2100 and rising 6 inches a decade, and another 2007 study from Nature Geoscience (“Sea levels may rise 5 feet by 2100“) that came to the same conclusion.

Chapter 3, “Hydrological Variability and Change,” concludes that subtropical aridity is likely to intensify and persist due to future greenhouse warming. This projected drying extends poleward into the United States Southwest, potentially increasing the likelihood of severe and persistent drought there in the future. If the model results are correct, this drying may have already begun.

The U.S. Southwest could see a permanent drying by the mid-21st century similar to the historic “megadroughts” that occurred from about A.D. 900 up to about A.D. 1600 – even though the cause of these previous droughts was not similar, as they occurred in a climate system “that was not being perturbed in a major way be humans.”