Record food prices, the destabilization of Egypt, and a cascade of catastrophic weather events across the world are all linked to the growing destabilization of the climate as global temperatures rise in response to increasing greenhouse gas levels.
Egypt is the world's largest importer of wheat. Food prices hit record highs in January, in response to the catastrophic drought in Russia and other extreme weather events that reduced the harvest of wheat and other staples. The destabilization of the governments of Tunisia and Egypt was triggered, in part, by the crushing effects of rapidly rising food prices on their populations.
Political destabilization, triggered by climate change, is rapidly becoming a key national security issue.
Multidisciplinary studies involving climatologists and archaeologists are developing detailed lines of evidence showing that human evolution was shaped by the changing climate in Africa. Climate and Evolution published in Science today on line.
Notable hominin extinction, speciation, and behavioral events appear to be associated with changes in African climate in the past 5 million years. First appearance and extinction events, as well as key behavioral milestones, cluster between 2.9 and 2.6 Ma and again between 1.9 and 1.6 Ma (see the figure, panel A). In the earlier group, these events include the extinction of Australopithecus afarensis ("Lucy") near 2.9 Ma; the emergence of the robust australopiths (Paranthropus spp.), with large jaws and grinding teeth, near 2.7 Ma; and the emergence of the larger-brained Homo lineage sometime after 2.6 Ma, near the time when the first evidence for Oldowan stone tool manufacture, use, and transport appears (10).
From 15,000 to 5000 years ago, the modern Saharan Desert was nearly completely vegetated, with large, permanent lakes and abundant fauna (14). Precessional increases in summer radiation invigorated the monsoon, delivering more rainfall deeper into Africa, and enhanced Nile river runoff flooded into the eastern Mediterranean Sea. The resulting freshwater stratification created anoxic conditions and led to deposition of organic-rich sediments (sapropels) on the seafloor. Stratigraphic sections representing many millions of years contain hundreds of these sapropel layers (15), and these layers are commonly bundled into 100,000- and 412,000-year packages associated with the modulation of orbital precession monsoon cycles with the eccentricity of Earth's orbit (see the figure, panel B). Many East African rift valley lakes in Ethiopia, Kenya, and Tanzania were high during a few, but not all, of these high-eccentricity intervals (see the figure, panel C) (16, 17).
The Saharan region was so wet that aquatic species migrated across it in preference to the Nile corridor.
Evidence increasingly suggests that sub-Saharan Africa is at the center of human evolution and understanding routes of dispersal "out of Africa" is thus becoming increasingly important. The Sahara Desert is considered by many to be an obstacle to these dispersals and a Nile corridor route has been proposed to cross it. Here we provide evidence that the Sahara was not an effective barrier and indicate how both animals and humans populated it during past humid phases. Analysis of the zoogeography of the Sahara shows that more animals crossed via this route than used the Nile corridor. Furthermore, many of these species are aquatic. This dispersal was possible because during the Holocene humid period the region contained a series of linked lakes, rivers, and inland deltas comprising a large interlinked waterway, channeling water and animals into and across the Sahara, thus facilitating these dispersals.
Now, human activities are changing the earth's radiation balance, by adding greenhouse gases to the atmosphere, at a far faster rate than natural orbital variations changed the radiation balance that drove glacial and interglacial cycles affecting human evolution.
The same amplifying effects, in particular the effects of changing the earth's reflectivity by melting (or increasing) ice and snow, that magnified minor orbital variations into the earth's glacial cycles are at work today.
Arctic sea ice extent averaged over January 2011 was 13.55 million square kilometers (5.23 million square miles). This was the lowest January ice extent recorded since satellite records began in 1979. It was 50,000 square kilometers (19,300 square miles) below the record low of 13.60 million square kilometers (5.25 million square miles), set in 2006, and 1.27 million square kilometers (490,000 square miles) below the 1979 to 2000 average.
Ice extent in January 2011 remained unusually low in Hudson Bay, Hudson Strait (between southern Baffin Island and Labrador), and Davis Strait (between Baffin Island and Greenland). Normally, these areas freeze over by late November, but this year Hudson Bay did not completely freeze over until mid-January. The Labrador Sea remains largely ice-free.
Air temperatures over much of the Arctic were 2 to 6 degrees Celsius (4 to 11 degrees Fahrenheit) above normal in January. Over the eastern Canadian Arctic Archipelago, Baffin Bay/Davis Strait and Labrador Sea, temperatures were at least 6 degrees Celsius (11 degrees Fahrenheit) higher than average. Temperatures were near average over the western Canadian Arctic Archipelago and Scandinavia.
As in December 2010, the warm temperatures in January came from two sources: unfrozen areas of the ocean continued to release heat to the atmosphere, and the wind patterns accompanying the negative phase of the Arctic oscillation brought warm air into the Arctic. Near the end of January the negative Arctic oscillation pattern broke down and turned positive, which usually favors ice growth.
January 2011 had the lowest ice extent for the month since the beginning of satellite records. The linear rate of decline for the month is –3.3% per decade.
This graph shows the ice extent in Hudson Bay from late November to the end of January, for the last five years. This year, Hudson Bay froze up substantially later than in previous years.
The NSDIC report explains how last year's and this year's cold winters in the eastern U.S. may be, in part, caused by the low Arctic sea ice levels.
Warm conditions in the Arctic and cold conditions in northern Europe and the U.S. are linked to the strong negative mode of the Arctic oscillation. Cold air is denser than warmer air, so it sits closer to the surface. Around the North Pole, this dense cold air causes a circular wind pattern called the polar vortex , which helps keep cold air trapped near the poles. When sea ice has not formed during autumn and winter, heat from the ocean escapes and warms the atmosphere. This may weaken the polar vortex and allow air to spill out of the Arctic and into mid-latitude regions in some years, bringing potentially cold winter weather to lower latitudes.
Some scientists have speculated that more frequent episodes of a negative Arctic Oscillation, and the stormy winters that result, are linked to the loss of sea ice in the Arctic. Dr. James Overland of NOAA Pacific Marine Environmental Laboratory (PMEL) recently noted a link between low sea ice and a weak polar vortex in 2005, 2008, and the past two winters, all years with very low September sea ice extent. Earlier work by Jennifer Francis of Rutgers University and colleagues also suggested a relationship between autumn sea ice levels and mid-latitude winter conditions.
Thus, one of the apparently unlikely affects of global warming might be, cold and snowy winters in the eastern United States.
A report published last week (just as the events in Egypt developed) in Science magazine stated that agriculture needed to included in the next round of climate negotiations.
Climate change and agriculture are inextricably linked.
Agriculture and Climate Change
Agriculture is a major source of CO2 emissions and contributes a disproportionate amount of other GHGs with high impact on warming [about 47% and 58% of total CH4 and N2O emissions, respectively (4)]. Of all global land area, 34% is used for food production (5), and this ties up a vast amount of carbon: Changes in agricultural practices that affect this store could have a considerable effect on global warming (6).
Climate change will affect our ability to produce food in multiple ways. Rising global temperatures and sea level together with changing patterns of precipitation will affect crop growth and livestock performance, as well as fisheries and aquaculture yields. Extreme weather events will become both more severe and more frequent, which will in turn increase volatility in production and prices. Some aspects of climate change may be beneficial to food production, but overall yields are highly likely to be reduced.