Tuesday, March 31, 2009

Taking Earth's Temperature

Average current global temperature = 55.04°F or 12.8 °C
source NOAA

 By Kristopher Hite

ResearchBlogging.orgWhenever evidence is presented for global climate change on a millennial time scale the method of choice seems to be polar ice. By measuring carbon dioxide in the tiny gas bubble captured in ice core strata from Antarctica researchers can generate graphs depicting earth's annual inhalation/exhalation of carbon dioxide for thousands of years. Al Gore famously displayed these results in an Inconvenient Truth while riding a hydraulic scissor lift next to his presentation showing how dramatically the green house gas levels have increased in recent years.

The beauty of the scientific method lies in how knowledge emerges. Knowledge is further validated or overturned when new evidence is presented. In the case of global climate change I suggest listening to scientists over George Will.

Researchers at the University of Arizona at Tucson recently published a paper brilliantly exhibiting an alternate method for measuring global temperature trends in the journal Nature Geoscience.

By using a freshwater lake on an island in the Galápagos as a natural laboratory these researchers where able to use the paleogeologic record to measure sea surface temperature trends. For thousands of years the lake had been collecting data in the deposits near the shore all the while waiting to be unearthed by some curious researchers.

The littoral zone in a fresh water lake consists of the shallow waters lining the perimeter. Unique microscopic communities live in this zone and differ from communities living in the deeper open water. When the clouds over the lake deliver more precipitation the lake gets deeper and the littoral zone shifts towards the shore. Think about looking down at a circular lake from above. If the littoral zone was colored it would look like the iris of a giant eye looking up at you. Warmer sea surface temperatures cause more rain and therefore the "iris" dilates while dryer times cause apparent constriction. As the creatures living in each zone die, dropping their remains to the lake bottom, they leave a series of horizontally stacked snapshots depicting the shifting littoral boundary. By taking cylindrical core samples from a lake depth in a fluctuating zone boundary and dating the strata the researchers were able to graph this dilation/contraction for two millenia.

Their results show that there has been UNPRECEDENTED warming of the sea surface temperature in the equatorial pacific ocean for the past 50 years. This provides the world a way to observe global climate change at the equator as well as the poles and further validates the idea that the globe, on average, is warming.

I recently heard a story in which a "human induced global warming" skeptic changed his mind as he watched for himself the shifting ecosystems near the arctic circle. I may be naive in thinking that piling on evidence in a case as monumentally important as climate change will redirect anyone's opinion, but I hope that logic works to persuade some global leaders before we have upwards of a billion climate refugees knocking on our doors.

Conroy, J., Restrepo, A., Overpeck, J., Steinitz-Kannan, M., Cole, J., Bush, M., & Colinvaux, P. (2008). Unprecedented recent warming of surface temperatures in the eastern tropical Pacific Ocean Nature Geoscience, 2 (1), 46-50 DOI: 10.1038/ngeo390
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