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This Week in Climate Science: “Unprecedented Heat,” Declining Snowpack, and Wildfire Feedbacks

By David Kroodsma

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 work that might not have been covered by major media outlets.

This week in climate science:

  • Extreme heat leads to more hospital admissions.
  • Snowpack has decreased in the Western US.
  • “Unprecedented Heat” may be the new normal in coming years.
  • How to improve REDD.
  • Energy efficiency improves reputation.
  • Wildfires cause an unexpected positive climate feedback.
  • Climate change and the eastern Mediterranean: impending water woes.

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Paper Title: The impact of extreme heat on morbidity in Milwaukee, Wisconsin
Journal: Climatic Change
Authors: Bo Li, Steve Sain, Linda O. Mearns, Henry A. Anderson, Sari Kovats, Kristie L. Ebi, Marni Y. V. Bekkedal, Marty S. Kanarek, and Jonathan A. Patz
The Gist: Warmer temperatures increase hospital visits.

Summary: Typically, studies of the health impacts of climate change estimate how warmer temperatures will increase the number of premature deaths (usually due to heat waves). However, few studies consider morbidity in terms of sickness and non-lethal hospital admissions. This study takes a unique look at how heat waves affect hospital visits in Milwaukee, Wisconsin. The researchers found that hot weather increased the number of people admitted for a range of illnesses, including kidney problems and diabetes.

The study also estimates that by the end of the 21st century, assuming a moderate level of global warming, hospital admissions will increase for a handful of diseases. The increase, though, is projected to be modest — less then 10 percent.


Paper Title: The Unusual Nature of Recent Snowpack Declines in the North American Cordillera
Journal: Science
Authors: Gregory T. Pederson, Stephen T. Gray, Connie A. Woodhouse, Julio L. Betancourt, Daniel B. Fagre, Jeremy S. Littell, Emma Watson, Brian H. Luckman, and Lisa J. Graumlich
The Gist: Snowpack in the Western US is declining at a rate that is nearly unprecedented in the past 800 years.

Summary: Spring snowpack in the West is, on average, about 10 percent less than it was three decades ago. But 30 years is not a long time when it comes to climate. Could the recent changes in spring snowpack be part of a natural cycle?
 
Fortunately, climate history can often be investigated using so-called "proxy records." For this study, researchers examined tree rings from old growth trees, since tree growth rings capture snapshots of past climate conditions. By analyzing the size and shape of these rings, researchers have estimated the amount of Western snowpack during the past 800 years, and found that the past few decades have been remarkably different.
 
Only twice in the past eight centuries has snowpack drecreased like it has during the past three decades, and both of those declines were less significant than today's. Climate Central’s Alyson Kenward wrote about this paper in more detail. The researchers suggest the decrease is largely due to warmer temperatures and the earlier onset of spring weather. Climate scientists expect these trends to continue during the next 100 years.


Paper Title: Observational and model evidence of global emergence of permanent, unprecedented heat in the 20th and 21st centuries
Journal: Climatic Change
Authors: Noah S. Diffenbaugh and Martin Scherer
The Gist: Beginning just a few decades from now, average summer weather in most areas of the globe will be similar to the hottest summers of the 20th century.

Summary: Think about what average summer temperatures are like in your neighborhood. Now, think about the hottest summer you can remember. In the future, what is now regarded as an unusually warm summer may be the norm, and researchers have recently established a timeline for when that could happen. 

Assuming that greenhouse gases keep building up in the atmosphere to the point that they double the pre-industrial level by 2050, the researchers found that average summer temperatures around the world will quickly increase. They found that the tropics are likely to be the first region where the new "average summer” would be warmer than the historic hottest summer. In fact, within the next 30 years, 70 percent of the tropics will have average summers that are warmer than the hottest summer of the late 20th century, according to this study.
 
This doesn’t mean that the amount of warming in the tropics will be greater than the amount of warming in polar regions — it won't be. But because year-to-year temperatures don't vary much in the tropics, a small amount of warming will push the system into a completely new climate.
 
Globally, by mid-century, many other regions will see average summer temperatures rise above the historic average highs, including the Western US, large areas of China, and much of Southern Europe.


Perspective: Painting the world REDD: addressing scientific barriers to monitoring emissions from tropical forests
Journal: Environmental Research Letters
Authors: Gregory P. Asner
The Gist: According to a new analysis, the so-called REDD program, which offers nations an incentive to preserve forests, lacks effective monitoring and verification.

Summary: In 2010, several countries agreed to a "REDD+" plan (REDD stands for: "Reducing Emissions from Deforestation and Forest Degredation") where wealthy nations pay developing countries to avoid deforestation. According to this perspective, however, no developing country has put in place an effective method to monitor deforestation. Moreover, a recent analysis showed that only three percent of tropical countries even have the capacity to monitor their forests.
 
Without accurate measurement, the author advises, it is nearly impossible to credibly reward countries. In this article, Asner, one of the world's experts in monitoring the state of forests, suggests several ways to help improve the REDD+ program.


Paper Title: The role of corporate reputation and employees’ values in the uptake of energy efficiency in office buildings
Journal: Energy Policy
Authors: Giuseppe Pellegrini-Masini, Chris Leishman
The Gist: When it comes to energy efficiency, companies are worried about their reputiation, not their bottom line.

Summary: Most businesses save money when they improve the energy efficiency of their offices, yet few companies adopt basic energy efficiency measures. In this paper, the authors survey building owners and occupiers in the United Kingdom. They find that most companies regard energy costs as a negligible part of doing business, and thus don't pursue energy efficiency measures.
 
A number of companies, though, are improving the efficiency of their offices, but they aren’t doing so to improve energy costs — the main motivating factor seems to be corporate responsibility. These businesses said efficiency reflected on the companies “values,” or indicated that they saw it as a way to improve their reputation. 


Paper Title: Global Change Could Amplify Fire Effects on Soil Greenhouse Gas Emissions
Journal: PLoS One
Authors: Audrey Niboyet, Jamie R. Brown, Paul Dijkstra, Joseph C. Blankinship, Paul W. Leadley, Xavier Le, Roux, Laure Barthes, Romain L. Barnard, Christopher B. Field, and Bruce A. Hungate
The Gist: In the years after a wildfire, burned soils release significant nitrous oxide, a potent greenhouse gas, thus amplifying climate change.

Summary: In July of 2003, an accidental fire burned a large portion of the Jasper Ridge Global Change Experiment — a testing ground that researchers use to study how plants adapt to all aspects of climate change. The fire, which at first seemed like a disaster, later proved to be an opportunity since it allowed the researchers to see how the ecosystem responded to wildfire.
 
Among other findings, they discovered that in the three years following the fire, the soils of burned land released twice as much nitrous oxide (N2O), a potent greenhouse gas, as land that had not been touched by fire. They also found that fire effects on soil emissions of this greenhouse gas were even larger when combined with higher carbon dioxide levels. Because wildfires are already becoming more prevalent and severe in a warming world, and since carbon dioxide levels will be higher in coming decades, this release of N2O represents a previously undocumented positive feedback to climate change (warming = more wildfires = more N2O released = more warming).
Unfortunately, the study doesn't estimate how large this feedback might be.


Paper Title: Impact of climate change on the water resources of the eastern Mediterranean and Middle East region: Modeled 21st century changes and implications
Journal: Water Resources Research
Author: Jonathan Chenoweth, Panos Hadjinicolaou, Adriana Bruggeman, Jos Lelieveld, Zev Levin, Manfred A. Lange, Elena Xoplaki, and Michalis Hadjikakou
The Gist: Climate change and population growth will make less water available in the eastern Mediterranean.

Summary: Climate scientists expect that the eastern Mediterranean will be significantly affected by future climate change, with many areas likely to see a 20 percent or more decrease in rainfall (according to an average of many different climate models, and assuming a moderate level of global warming). 

This study modeled future water resources, assuming a moderate level of global warming, in 18 countries between southeast Europe and Iraq. The authors projected population growth and estimated how much water would be available per person in the final three decades of this century. Because of high population growth, countries in the Middle East are expected to be more significantly affected than those in Southeast Europe. The countries that will experience the most water stress are Turkey, Iraq, Syria, and Jordan.