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This Week in Climate Science: Better Biofuels, Climate Extinction, and Global Warming Slowdown

By David Kroodsma

Credit: David Reber/Flickr.

Welcome to Climate Central’s climate science roundup. This roundup summarizes noteworthy climate science studies published in the previous two weeks, with a special emphasis on articles that might not have been covered by major media outlets.

This week in climate science:

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Paper Title: Reconciling anthropogenic climate change with observed temperature 1998–2008
Journal: PNAS
Authors: Robert K. Kaufmann, Heikki Kauppi, Michael L. Mann, and James H. Stock
The Gist: Sulfur pollution from coal-fired power plants may have contributed to a slower rate of global warming between 1998 and 2008.

Summary: If you look at how global temperatures have changed recently, you’ll see that in the decade following the extremely warm year of 1998, global warming slowed down. But over that same time period, global greenhouse gas emissions increased significantly. Does that mean we don’t need to worry about future climate change?
This study investigates what else might have affected global temperature trends between 1998 and 2008 (in addition to natural variability). It turns out that, since 1998, an increase in sulfur pollution, largely from a boom in Chinese coal power plants, may have temporarily compensated for much of the impact of increasing greenhouse gas concentrations. The sulfur particles, known as sulfate aerosols, reflect sunlight back to space, thus cooling the planet. This doesn’t mean that global warming will stop altogether, though. These sulfur particles don’t stay in the atmosphere long, while greenhouse gases do, meaning that warming is expected to take off again in the coming years — indeed there are indications this is already taking place. Check out a great story on this paper by Climate Central's Mike Lemonick.

Paper Title: Recent ecological responses to climate change support predictions of high extinction risk
Journal: PNAS
Authors: Ilya M. D. Maclean and Robert J. Wilson
Credit: Federi/Flickr.
The Gist: Climate change will likely cause widespread extinctions of both plants and animals — perhaps even more than researchers previously thought.

Summary: How many plants and animals will go extinct because of climate change-related changes to their environment? Scientists have published many papers trying to answer this question, but their results are contradictory: some suggest an extinction rate of just few percent, while others estimate that with higher levels of warming, more than forty percent of all species could be at risk.
This new study approaches this question in two novel ways. First, it surveys all existing studies and averages the results, finding that, on average, scientists estimate about 10 percent of species are at risk. Secondly, it uses data from the International Union for Conservation of Nature to compare how climate change has already affected populations. They then extrapolate extinction rates from those estimates. The new data suggests a higher extinction rate of about 14 percent.
In general, marine species are at greater risk than land-based plants and animals, largely because coral reefs are particularly susceptible to climate change. Moreover, species in temperate and northern regions are more at risk than those closer to the equator.
But of course, this is still just an estimate. No one really knows how entire ecosystems will respond to climate change.

Paper Title: Warming increases the spread of an invasive thistle
Journal: PLoS One
Authors: Rui Zhang, Eelke Jongejans, Katriona Shea
The Gist: Climate change will increase the mobility of musk thistle, an invasive species in the eastern U.S. and Canada.

Summary: Will invasive plant species become more or less common under climate change? The answer is not straightforward, largely because each species will respond differently. (Although some studies have suggested that, on balance, invasive species will benefit from climate change-related shifts in environmental conditions.)
This study tries to answer the question for musk thistle,(Carduus nutans), a purple flower native to Europe that has spread across eastern North America. It is a nuisance to livestock owners, as it crowds out native species and its spiny leaves make it unsuitable for grazing. The thistle spreads much like a dandelion, by letting the wind carry its seeds.
In a Pennsylvania field, researchers put the plants in heated chambers to simulate climate change. They also added extra water to mimic an increase in rainfall, a possible outcome of climate change in Pennsylvania.
It turns out the thistle thrived in the simulated warmer and wetter conditions: seeds were more likely to sprout, they sprouted earlier, and the resulting plant grew taller. The increase in height is an important trend, as it allows the seeds to disperse about twenty five percent farther than under normal conditions, increasing the plant’s spread.
Of course, the study didn’t fumigate the plants with carbon dioxide to simulate the higher future levels of CO2, and its findings are hardly conclusive.Nonetheless, it suggests that this invasive specie will benefit from a warming planet.


Credit: bongo vongo/Flickr.

The Gist: During summers in Europe, the Rhine, Rhone, Po, and Danube rivers are fed from glacial runoff in the Alps. But researchers expect that warming temperatures are causing glaciers to melt to such a large extent that river flow could be dramatically altered.

Summary: Melting mountain glaciers are a well-known manifestation of climate change, and most of us have seen images of how much glaciers have shrunk in the past century. But if climate change continues to cause mountain glaciers to melt, there could be serious consequences for nearby rivers that feed off of summer meltwater.
This study estimates the contribution of the Alps’ glaciers to the Rhine, Rhone, Po, and Danube Rivers over the 20th century and then models river flow during the next century.The authors estimate that by 2100, about 90 percent of the Alps’ glaciers will disappear. With almost no glaciers left, the water flowing off them will be drastically reduced.
It’s important to point out here that because these four rivers cover such large areas, only a small amount of their total flow comes from glacial runoff. For instance, at the Rhine’s mouth, in the month of greatest glacial melt (August), glacial water is only about seven percent of the river flow. But up in the mountains, most of the river flow does originate from glaciers.

Paper Title: Impact of second-generation biofuel agriculture on greenhouse-gas emissions in the corn-growing regions of the US
Journal: Frontiers in Ecology and the Environment
Authors: Sarah C Davis, William J Parton, Stephen J Del Grosso, Cindy Keough, Ernest Marx, Paul R Adler, and Evan H DeLucia
The Gist: Growing grasses to produce ethanol fuel produces fewer greenhouse gas emissions than growing corn for the same purpose.

Summary: You probably didn’t know that only eight percent of corn grown in the U.S. feeds humans. Most of the rest of it goes to feeding livestock and producing corn ethanol. Ethanol sounds like a clean fuel, but producing it from corn produces almost as many greenhouse gases burning regular gasoline. What if all the corn crops used to make ethanol were replanted with a different crop that could provide the ethanol in a less greenhouse gas intensive manner? According to this study, some types of grasses can provide the same amount of ethanol fuel without nearly as much pollution.
For example, if miscanthus, a perennial grass, replaced 30 percent of the nation’s corn, it would reduce greenhouse gas pollution by about 430 million tons of carbon dioxide equivalent per year. This is because the crop stores significant amounts of carbon in the soil, and doesn’t require much fertilizer. Overall, that savings equals roughly six percent of total U.S. emissions. Not only that, ethanol production would roughly double by growing miscanthus, meaning that the carbon savings would be even greater.
On the other hand, this study ignores a pretty important question: how much would it cost to grow miscanthus? If it can be made cost effective, than we may soon see these perennial grasses across the U.S. Midwest.



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