Climate Change, Nature, Science

‘Global Thermometer’ Is Tracking Temperature Extremes

A tropical area during low-water season.
Droughts in the tropics are just one consequence of rising global land temperatures. Photo: Shutterstock

According to a paper published in the Journal of Applied Meteorology and Climatology, large areas of the earth are experiencing rising maximum temperatures.

This may sound like a no-brainer, given that we’re in an era of unprecedented global warming, but the conclusions drawn through this research are based on changes in land surface temperatures rather than changes in air and water temperatures.

The researchers analyzed records from NASA’s Aqua satellite between 2003 and 2014 and found spikes in maximum surface temperatures occurred in the tropical forests of Africa and South America and in much of Europe and Asia in 2010, and in Greenland in 2012. These measurements coincided with phenomena including severe droughts in the tropics and heat waves and wildfires across the northern hemisphere. The 2012 land surface temperature spike in Greenland was associated with massive melting of the Greenland ice sheet.

What exactly is land surface temperature? It’s a measurement of the heat radiated by land—including soil, rock, and pavement—and vegetation such as trees and grass. Weather stations generally measure air temperatures just above the surface, so the satellite readings of land surface temperature are critically important in the study of global climate change.

“Imagine the difference between the temperature of the sand and the air at the beach on a hot summer day,” said study lead author David Mildrexler, who received his Ph.D. from Oregon State University. “The air might be warm, but if you walk barefoot across the sand, it’s the searing hot surface temperature that’s burning your feet. That’s what the satellites are measuring.”

The researchers studied annual maximum land surface temperatures averaged across 8-day periods throughout the year. They used data from the Aqua satellite, which crosses the equator in the early afternoon as temperatures reach their daily peak.

“As anyone who pays attention to the weather knows, the Earth’s temperature has incredible variability,” Mildrexler said. However, he added, the planet’s profile of high temperatures tends to be fairly stable from year to year. The researchers’ discovery of a consistent year-to-year profile allowed them to develop a new global-change indicator that uses the entire planet’s maximum land surface temperatures.

“The maximum surface temperature profile is a fundamental characteristic of the Earth system, and these temperatures can tell us a lot about changes to the globe,” said Mildrexler. “It’s clear that the bulk shifts we’re seeing in these maximum temperatures are correlated with major changes to the biosphere. With global temperatures projected to continue rising, tracking shifts in maximum temperature patterns and the consequences to Earth’s ecosystems every year globally is potentially an important new means of monitoring biospheric change.”

In other words, this new research supports the conclusions of a whopping 97 percent of scientists, who believe that global climate change is real, and it’s happening fast, and we need to do something to mitigate that before we reach a point of no return.

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