Probabilities reveal shape of climate change

Planners looking to prepare for floods, like this one in Venice, Italy, would like better local information on climate change – and now David Stainforth and his colleagues are helping deliver it. Image courtesy http://www.WorldIslandInfo.com, Allison Lince-Bentley, used under Flickr Creative Commons license.

If you want to plan for the future, or even for the present, knowing that our climate is changing, what’s the best way to do it? That’s a question that David Stainforth from the London School of Economics, Sandra Chapman from the University of Warwick and Nicholas Watkins from the British Antarctic Survey have puzzled over. And while David is co-founder of the climateprediction.net project that borrows spare time on peoples’ computers to run climate models, he doesn’t feel that models are always the best source of information.

“It’s clear to me that the detailed local information on how climate is changing, and what it will be like in 2050, can’t be had from climate models today,” David told me. “They’re just not that good. And yet I work a lot with the adaptation and impacts community, who are interested in what’s happening ‘here’, on a very local basis.” So together David, Sandra and Nicholas have turned to measured data, devising a simple way to pick the most important local climate changes from it.

Weather stations around the world monitor daily conditions, and combine to create a record containing occasional extremes, lots of ordinary days, and everything in between. Knowing how common these conditions are is important for people who want to prepare for future climate change. “For flood risks, you’re worried about going over certain rainfall amounts in a given time,” David explained. “Managers of overheating buildings are worried about what proportion of the time temperatures pass certain levels.”

Mild winters raise risk of flu epidemics

Arizona State University mathematician Sherry Towers has found links between a warm winters with little flu to epidemics the following year. Credit: Arizona State University

In 2012/13 the US flu season started especially early for two strains for the first time since the government started tracking it in 1997. Sherry Towers at Arizona State University has put this down to the unusually warm winter the country saw in 2011/2012, after showing such a link can be seen in previous years. She hopes that her findings can help health services prepare as winters get yet milder with continuing climate change.

“Until now, it had not been noticed that the dynamics of the current season depend not only on the temperature of the current season and vaccine match, but also on what had occurred the year before,” Sherry told me. “If there has been a mild flu season during a mild winter, public health authorities know several months in advance that a severe season with early onset is much more likely to occur the next season. This allows them to expedite the manufacture and distribution of vaccines to the population.”

As a mathematician looking at how climate affects the spread of infectious diseases, Sherry follows influenza data collected by the US Centres for Disease Control (CDC) closely. The CDC tracks the various influenza virus types in circulation. These include letter and number combinations you might have heard, like H1N1 and H3N2, which together are classed as influenza A, plus the single type of influenza B virus. Scientists had previously shown that high temperatures reduce transmission of the virus, which alone would make mild flu seasons more common in warm winters. Though this suggests less of a threat from flu in a warmer world, this season’s data made her wonder if there could be a downside.

CO2 casts off shackles to power up Atlantic hurricanes

NOAA’s GOES-13 satellite captured this visible image of Hurricane Sandy battering the U.S. East coast on Monday, Oct. 29 at 9:10 am EDT. Sandy’s center was about 310 miles south-southeast of New York City. Tropical Storm force winds are about 1,000 miles in diameter, and are set to intensify in the 21st century. Credit: NASA GOES Project

Changes in greenhouse gases and other air pollution will likely make Atlantic storms that could hit the Caribbean and Eastern US more intense through this century. That’s according to research from Gabriel Vecchi at the US National Oceanographic and Atmospheric Administration (NOAA) in Princeton, New Jersey, and Gabriele Villarini at the University of Iowa. They’ve found that more greenhouse gases strengthen these storms but other pollutants known as aerosols or particulates, which include soot, do the opposite. Increases in both types of pollution through the 20^th century therefore cancelled each other out. But with more recent efforts to limit aerosol pollution succeeding, Atlantic storms now look set to become more destructive. “Both reductions in particulate pollution and increases in greenhouse gases are going to co-operate, we think, to give us more intense hurricanes in the Atlantic,” Gabriel said.

Gabriel has long studied Atlantic storms, and together with Gabriele recently found that how often they happen will likely only increase during the first half of the 21^st century. “The number of storms in a season is only part of the story,” Gabriel told me. “A big question for society is the intensity.” So it was natural, he added, to follow on by looking at how strong and long-lasting they are. Scientists have already looked at their intensity for narrow “time-slices”, for example from 1985-2005 and then predicting from 2080 to 2100. “People haven’t explored how we go from the late 20^th century to the late 21^st century,” Gabriel said.” That’s because to do this research they need complex and very detailed ‘high resolution dynamical’ climate models, which use up scarce time on the world’s most powerful computers. For the same reason, previous studies only look at a few possible scenarios for how much of the greenhouse gas CO2 humans will produce by burning fossil fuels.

Monsoon instability raises food questions for India

A street in Calcutta floods during monsoon season. After some decades of increasing rainfall, climate change could bring drier monsoons, said Jacob Schewe from the Potsdam Institute for Climate Impact Research. Credit: Mark E Dyer/Flickr

Monsoon rains in India may fail more frequently as climate change proceeds into the 22^nd century, German researchers said this week. That danger could be critical for farming in what is set to become the world’s most highly populated country by 2030, and would follow an already expected wetter period. “Previous studies showed that Indian monsoon rainfall would increase more or less linearly with global warming over the next century,” said Jacob Schewe from the Potsdam Institute for Climate Impact Research. “The monsoon can respond to climate change in a more complicated way. We’ve seen that it matters to look further into the future.”

In South Asia, summer monsoon rains fall as winds blow from the southwest Indian Ocean over the continent between June and September. They end when the wind direction reverses in September or October. What Indian monsoon rain seasons will do as the world warms is an important and difficult question that many researchers are trying to answer. Though more rainfall has been predicted, recent years haven’t matched that expectation. While factors like pollution have an effect, changes climate scientists already know a major climate pattern plays a very important part in monsoons.

“There is a coupling between the El Niño Southern Oscillation and the monsoon that’s been observed for a long time,” Jacob told me. In years when El Niño occurs, an air movement pattern called the Walker circulation pattern gets shifted eastward. That brings high pressure over India and weakens the monsoon. While some changes in El Niño are already happening, the Walker circulation is expected to weaken, but not for some time yet. That could mean scientists’ climate models don’t pick up its effects. “People have looked at monsoon changes but not many studies have looked beyond 2100,” Jacob said. “You really have to consider longer timescales – beyond 2100 – to assess the full range of consequences for the monsoon.”

Temperature rises could hamper developing world growth

Higher temperatures can lower productivity in non air-conditioned factories like this one owned by bead manufacturer Kazuya in Nairobi, Kenya, says MIT’s Ben Olken. Credit: Amy the Nurse/Flickr

Higher temperatures play a role in economic progress that brings bad news for poorer countries. Their development efforts may be slowed as the world warms further, suggest researchers at the Massachusetts Institute of Technology (MIT) and Northwestern University in Evanston, Illinois. Looking at over 50 years of weather data, MIT’s Ben Olken and his colleagues showed that every 1°C temperature increase shaves 1.3 percent off a poor country’s growth, over the course of a given year. That can have a big impact, considering the World Bank projects that developing countries’ economies will grow by 5.4 percent in 2012. “The key points of our study for thinking about climate change are that a) the impact seems to be larger for poorer countries and b) there is at least the possibility that the economic magnitude of the costs of higher temperatures for poorer countries could be quite large,” he told Simple Climate.

People have been asking whether temperature influences how rich a country is for centuries, with historian Ibn Khaldun discussing it in his book Muqaddimah in 1377. But researchers are still trying to tease out the various ways it can play a part even today. Getting a grip on this subject becomes more important as the world warms in response to human CO2 emissions, Ben noted. “Given the interest in global climate change, the link between temperature and economic growth is clearly important to understand,” he said. “While there are many studies that try to simulate these impacts, we thought it was very important to try to look, historically, at what actually happens when it gets warmer. When we thought of doing this, we were very surprised that nobody had really done it before.”

Ben, MIT’s Melissa Dell and Northwestern’s Ben Jones brought together temperature, rainfall and economic output data for 1950-2003 from 125 countries. In a paper published in the July edition of the American Economic Journal: Macroeconomics they compared temperature and rainfall changes against economic growth. By studying year-to-year changes they could avoid assumptions about what links exist and remove the effects of unchanging national factors. Looking at economic growth both in the same year as the weather data and up to ten years later allowed them to see how long any impacts lasted. While economic growth in poor countries was affected by temperature, there was little effect on growth in rich countries. Changes in rainfall have relatively mild effects on national growth in both rich and poor countries. Their data showed that these were permanent effects on growth, rather than temporary dips in output after which the countries continued the progress they were making before.

CO2-focused breeding can arm crops for food fight

Growth of modern farmed rice varieties rise proportionally less when CO2 levels go up than wild types. Lewis Ziska and his colleagues said that more effort needs to be made in plant breeding to make sure crops benefit from higher CO2 levels. Credit: Héctor de Pereda/Flickr

While CO2 emissions from humans burning fossil fuels are wrapping the world in a worryingly warming blanket, they could also help make our crops grow faster. But more direct effort is needed to make the most of this chance, say Lewis Ziska from the US Department of Agriculture and an international team of scientists. “Plant breeders often assume that on-going breeding efforts, for example for pest or disease resistance, would by themselves lead to adaptation to any rise in background CO2 levels,” Lewis told Simple Climate. “We’ve shown that this is not the case.”

Throughout the 20^th century crop breeding has been one part of a green revolution that has made farmers today able to produce much more food from their fields. But Ziska notes that these improvements in crop yields are slowing. Though climate change and the droughts it brings makes this problem even harder, the gas driving it could provide a way out.

“The gains of the green revolution with respect to population growth have ended,” Ziska said. “As agricultural scientists our goal is to ensure a safe and nutritious supply of food.  It is clear we will have to do so with fewer resources, specifically arable land, water and fertilizer. We have long recognized that CO2 is, by itself, a resource as it supplies plants with carbon, the basic building block for growth. Hence we are urging a systematic active effort in selecting cereal lines that could respond to rising CO2 levels by increasing their yields.”

This view springs from a wide range of evidence Ziska and his colleagues brought together in a paper published in the research journal Proceedings of the Royal Society B this week. This included Ziska’s own research showing how CO2 concentrations affected wheat bred during the 20^th century, when CO2 rose from around 290 parts per million (ppm) to 380 ppm. That study showed that higher CO2 concentrations increased the amount of wheat produced by forms developed nearer to 1900 more than modern varieties.

Hotter summers set to make power generators sweat

The Browns Ferry Nuclear Plant in Alabama uses water from the Tennessee River for cooling. Credit: Tennessee Valley Authority

Even as fossil-fuel power stations emit CO2 and drive climate change, they will likely generate less electricity in a warmer world. Both fossil fuel and nuclear electricity generation plants have already been affected by higher water temperatures and reduced river flows. And in the future the same problems could mean that summer average generation capacity could fall by one-twentieth to one-fifth from past levels. So says the largest study yet of climate change’s effect on cooling water used in power generation, by Michelle van Vliet from Wageningen University in the Netherlands and her colleagues.

“Our results show overall increases in river water temperature under climate change, with highest increases in the southern part of Europe and south-eastern part of the US,” Michelle told Simple Climate. “For large parts of the US and Europe the results show an overall increase in high river flow and decreases in low river flow. The combination of higher water temperatures and lower river flows during summer periods can be especially critical for cooling water use.”

Nuclear or fossil fuel plants with water cooling currently produce over three out of every four units of electricity consumed in Europe and over nine out of every ten in the US.  They use more river water than farming and more than twice as much as the demand from homes in each region. That thirst poses these “thermoelectric” power stations problems in a warming world, Michelle explained. “Due to climate change, periods with low river flows in combination with high water temperatures are expected to occur more often, and this could cause significant reductions in cooling water availability during summer,” she said.

Warming brings more frequent and fickle European heatwaves

Heatwaves prompt creative ways to stay cool, as these children in Paris showed during the 2003 heatwave, and can lead to deadly consequences if people don’t stay cool enough, especially amongst the elderly. Credit: Christophe Becker/Flickr

Our changing climate will make future European summer heatwaves like the one in 2003, blamed for killing 35,000, more likely but harder to forecast a season in advance. That’s what research done by Benjamin Quesada from the Laboratoire des Sciences du Climat et de l’Environnement (LSCE) in Gif-sur-Yvette, France, suggests. Together with fellow climatologists, he has found that water trapped in Southern European soil during wet winters and springs keeps the continent reliably cool in summer. “Under global warming, climate models almost all agree about drier soils in Southern Europe and more frequent and long lasting summer heatwaves,” Benjamin told Simple Climate. Losing that cooling influence currently makes the weather less predictable but with a higher chance of being hot – though Benjamin hopes his findings will eventually bring more accurate forecasts.

The dramatic heatwaves in 2003 and 2010 took Europe by surprise. That has motivated the continent’s scientists to try to understand them and therefore predict them better. The role that water absorbed in soil plays has been one area that they’ve looked at. Their research shows a vicious “feedback” cycle where drier soils mean that less water reaches the atmosphere to create clouds. In turn, more heat from the sun reaches the ground and dries it out yet more. “Soil moisture can be seen as a buffer,” Benjamin said. “On dry soil, solar energy will directly heat soil, and isn’t ‘wasted’ first in evaporation as in wet soil.” Usually an escape from this cycle can come thanks to factors like winds circling the planet and carrying clouds with them, he added.

Volunteer computers broaden climate model forecasts

Climate Researcher Dan Rowlands. Credit: Oxford University

Possible world temperatures in 2050 cover a wider range than previous official forecasts suggest, with the increase on the hotter side, scientists have said this week. That conclusion is based on a massive experiment, running 10,000 simulations using donated time on more than 30,000 computers through the climateprediction.net project. “The warming could be nearer to 3ºC rather than 2ºC higher than the average from 1961-1990 by 2050,” said Oxford University researcher Dan Rowlands.

Today, the most used predictions for future climate come from the Intergovernmental Panel on Climate Change (IPCC). The IPCC brought together models from around 20 of the best groups in the world doing research in this area in the Climate Model Intercomparison Project phase three, or CMIP3. But with such a small number of models, they couldn’t explore the range of future temperatures well.

“The IPCC knows this,” Rowlands told Simple Climate. “So, its uncertainty estimate is based on results from much simpler climate models. A lot of people have questioned whether they’re missing a lot of the key processes that might become important as the climate changes.”

But to predict what climate change will do to the world in detail, scientists need models like those used in CMIP3. “Say you’re looking at flooding in the UK in 2050, you need some meteorological drivers to put into your flood model from these large, complex, climate simulations,” Rowlands explained. “People in that field basically use the range from CMIP3, because that’s all that exists. We wanted to go out and challenge the uncertainty range of warming projected in CMIP3.”

Building climate adaptation on flooded fields

Emma Tompkins from the University of Southampton has been studying why people do things that help their whole community adapt to climate change. Credit: International Institute for Sustainable Development

Even as many governments seem too paralysed to act on climate change, some people and organisations are beginning to adapt to its challenges and threats. And there are cases where their efforts are providing benefits that can be enjoyed by their communities, without receiving any financial reward. While such acts currently don’t get much attention, Emma Tompkins from the University of Southampton, UK, and Hallie Eakin from Arizona State University think they’re fairly common. Emma told me that private actions like farmers allowing their fields to flood to protect more developed areas downstream could be worth millions. “The cost of adapting to climate change could be significantly reduced if we can harness that, and encourage greater provision of these public goods,” she said.

When Hallie and Emma first met, they were surprised to find that they both knew cases where people were acting in this way. Emma had heard tell of farmers in the UK and France who let their fields be flooded to protect others. Meanwhile Hallie knew that small coffee growers in Mexico deliberately encouraged a greater variety of plants to increase soil stability and reduce the risk of landslides in an area prone to hurricanes. “We then became increasingly interested and started finding evidence it wasn’t just the two of us having