Research you may have missed over the holidays
Here are a few of the latest updates in climate science you may have missed over the last couple of weeks:
The Arctic is losing huge amounts of ice every second
Melting Arctic glaciers are pouring a whopping 14,000 tons of liquid water into the sea every second, according to a study published last month in Environmental Research Letters. That makes the Arctic region — including Greenland; Iceland; and parts of Canada, Alaska and Russia — the biggest current contributor to global sea-level rise, more significant even than the far larger Antarctic ice sheet.
The study, which focuses on the period from 1971 to the present, suggests that the rate of ice loss has accelerated over the last few decades as the climate has continued to warm. The Arctic alone is now contributing to more than a millimeter of sea-level rise each year.
An Antarctic mystery solved?
Unlike Arctic sea ice, which has been steadily declining for decades, Antarctic sea ice was actually expanding until recently. Then, in 2016, it took a sudden and dramatic nosedive — much to the confusion of climate scientists.
Just this week, two studies in Nature Communications have offered some insight into what may have happened.
Both papers suggest the unexpected decline was driven in part by unusually high temperatures and heavy precipitation in the Indian Ocean, which helped create a pattern of atmospheric waves that affected winds as far south as the Southern Ocean. These changes in wind patterns helped drive down the sea ice extent around Antarctica.
The studies note that other natural climate variations affecting Antarctica also likely played a role in the sea ice shift. But human-caused climate change may be partly to blame, as well. The second study points out that an ongoing warming trend in the Indian Ocean probably helped set up the conditions that made the 2016 event possible.
Click here for the first study and here for the second.
Evidence grows against the global warming ‘pause’
The idea of a global warming “hiatus” in the late 1990s and 2000s has inspired some of the greatest debate in recent climate science history.
The idea, which experts say first cropped up around 2013, suggests that data indicate there may have been a 10- to 15-year slowdown or pause in global warming, which resumed pace again in 2012. The idea was heavily seized upon by doubters of mainstream climate science at the time.
The notion has inspired dozens of scientific papers over the last few years. Many researchers have since concluded that there was never any hiatus, or that while there may have been a temporary fluctuation in global temperature patterns, it’s all still consistent with the long-term trend of planetary warming.
Last month, two new studies — both published in Environmental Research Letters — tackled the idea once again.
One study conducts statistical tests on the pause period, placing it in the context of historical observed temperatures. The other compares historical observations with model simulations to determine whether there was any significant difference between what happened during the hiatus period and what should have happened in a world where global warming progresses as expected.
Both studies concluded that there’s no statistical case for a global warming pause.
“The results of our rigorous investigation in both studies are as simple as unambiguous: There was no pause in global warming,” climate researcher Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research, a co-author on both studies, said in a statement. “And global warming did not fall short of what climate models predicted.”
Bioenergy could help the climate but hurt the environment
The expansion of bioenergy — growing plants to burn for energy or to convert into fuels — is a widely proposed idea to mitigate climate change. But in recent years, many studies have warned that the amount of land it would require on a global scale in order to make a significant difference could be harmful to the world’s natural ecosystems.
Some research suggests it could use up huge amounts of water, drive deforestation and encroach on important wildlife habitat. Finding a sustainable balance among these conflicts — if there is one — is now an important component of bioenergy research.
At the end of last month, a paper in Proceedings of the National Academy of Sciences adds another warning to the list of possible consequences of bioenergy expansion. The land use changes it would require could cause substantial damage to the world’s birds, amphibians and mammals — enough to outweigh any benefits those animals might gain from the climate impacts of bioenergy.
The authors conclude that “biodiversity is likely to suffer severely if bioenergy cropland expansion remains a major compo