2 Studies Add Heavy Weight to Climate Understanding

Photo: NASA

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The Earth's atmosphere hasn't had this high a concentration of greenhouse gases in the 800,000-year record locked in Antarctic ice, according to one new study. And those heat-trapping gases have fueled vast changes to the Earth's surface that have now been documented in greater detail, according to a second. Both will be published in Nature.

The new ice-core data from the University of Berne adds 150,000 years to the climate record, which scientists measure by analyzing the gases trapped in bubbles, according to Reuters. The concentration of carbon dioxide is 28% greater than any time in the last 800,000 years, and the concentration of methane – a less abundant but more powerful greenhouse gas – is 124% greater.

Both gases add carbon to the atmosphere, where it traps heat at the Earth's surface.

The second study, involving a high-level team of international scientists, shows how dramatically that excess heat has already affected life on Earth since 1970. (The increase in temperatures in the past 35 years has been more dramatic in part because the rate of pollution of greenhouse gases has increased dramatically and in part because the rate of other climate-cooling pollution – like sulfur, chlorofluorocarbons and particulates, which cause acid rain, ozone layer depletion and lung disease, respectively – has declined.)

"This is the first study to link global temperature data sets, climate model results, and observed changes in a broad range of physical and biological systems to show the link between humans, climate, and impacts," said NASA's Cynthia Rosenzweig, lead author of the study.

Among the changes the study attributed to global warming: glaciers shrinking, permafrost melting, and lakes and rivers warming. The growing season is longer, plants leaf out and flower earlier, birds migrate earlier in spring, and heat-intolerant species are migrating up mountain slopes and toward more extreme latitudes. Oceans food webs also show a distinct shift.

Those may sound familiar to people who have read about climate change. What sets this study apart is the degree of detail from a number of data sets, which adds significant weight to the idea that global warming has caused significant changes. Because carbon is long-lived in the atmosphere, the world has bought several decades of additional warming that will occur even if emissions stopped completely today.

Before industrial times, the carbon dioxide concentration in the atmosphere ranged from 172 to about 300 parts per million, according to the first study. It is now at 380 ppm.

Overall, according to the second study, 90% of observed changes to the world's physical and biological systems are consistent with warming.

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