Cave deposits reveal permafrost concern

University of Oxford’s Anton Vaks explores a cave, where he could find stalactites and stalagmites that reveal when the soil above was permafrost. Credit: University of Oxford

Stalagmite and stalactite deposits in Siberian and Mongolian caves have revealed the most accurate permafrost history yet, suggesting that a global 1.5°C temperature rise could trigger a widespread thaw. “The finding shows how vulnerable the permafrost is,” said Anton Vaks from the University of Oxford. “Russian gas facilities in north-western Siberia are located close to the boundary of the continuous permafrost and rely on it as hard ground. Thawing of the permafrost may cause damage both to Russia, as well as its gas trade partners, like the European Union. The melting permafrost may also release part of the organic carbon currently trapped in it as greenhouse gases, CO2 and methane, enhancing global warming.”

Anton first used cave deposits’ power to study climate history during his PhD to build a 350,000 year record for the northern margin of the Saharan-Arabian Desert. “Stalagmites and stalactites grow only when rain or snowmelt water seep into the cave through the ceiling,” Anton explained. “Therefore each layer of growth of stalagmites and stalactites records a humid event in the desert.” He realised that these deposits’ ability to track water flow could equally measure melting of previously permanently frozen soil known as permafrost. “Cave deposits cannot grow when the rock above the cave is frozen,” Anton said. “Thus, each growth layer in a stalagmite forms during warm periods, whereas growth breaks represent cold periods with permafrost. Past periods that were warmer than now are especially important, because they can show what may happen to the permafrost in the future warmer world.”

Extra stations bolster warming-extreme rainfall link

The highest daily rainfall in a year is increasing by around 7% per 1°C warming. Credit: Andrew Ciscel via Flickr

The most comprehensive review of changes to extreme rainfall yet has confirmed the link between extreme rainfall intensity and global atmospheric temperature, with annual rainfall highs intensifying by around 7% per 1°C warming. University of Adelaide’s Seth Westra and his teammates called on 8326 weather stations across the Earth’s surface with over 30 years’ data from the period between 1900 and 2009. “The real innovation in this study is the strength of the data set we used,” Seth told me.

As a flood engineer, Seth has conducted numerous flood risk studies using highest daily rainfall amounts over a year period for planning. But when trying to understand how these rainfall amounts are changing, he found that many studies did not present their information so engineers could use it easily. He therefore wanted to do a statistical study that could produce more precise estimates. And when he found out that Lisa Alexander at the University of New South Wales, Australia was bringing together measurements of temperature and rainfall extremes, he saw his opportunity.

Lisa is part of a team that has collected data from 11391 weather stations worldwide, a much larger record than previous studies had used. That’s partly to contribute to the Intergovernmental Panel on Climate Change’s fifth assessment report on global warming, due out in stages in late 2013 and 2014. But it meant the massive task of collecting the measurements needed to do the kind of study Seth planned was already being done. “You can imagine the sheer amount of work in getting data from dozens of meteorological agencies from around the world,” he said. “Trying to feed them all into one single repository is a lot of effort.”

With this data in hand, Seth, Lisa and Francis Zwiers from the University of Victoria, Canada, first selected only the 8326 stations with over 30 years’ worth of data. They then used two statistical tests to look at the annual extreme rainfall highs, which they published online last year in a paper in the Journal of Climate. In the first, they simply looked at whether rainfall extremes increase or decrease at each station over time, Seth explained.

Climate limits room at the global dinner table

Reducing tillage used to prepare soil in farming can help reduce carbon emissions without also reducing crop yields. Credit: USDA Natural Resources Conservation Service

Part two of two

Another mid-winter feast has passed since I published the first part of this round-up of research linking food and global warming, its memory still pleasantly fresh in my mind. I’d hate to have to sacrifice any of it in the future. But what if I were forced to change or shrink my menu? You might not have to make these choices today, but scientists are helping farming adapt to a changing climate. They’re facing up to a big challenge: trying to reduce emissions, while maintaining food supplies.

As well as being affected by climate change, farming also produces some of the greenhouse gases that cause it – between one-tenth and one-third of the world’s emissions. Agricultural consultant Rob Carlton and his colleagues therefore looked at four different crop farming methods in March last year to see which would emit least greenhouse gas if the whole UK adopted it. The best approach was to dig up less left over plant material than conventional farming currently does, keeping more carbon trapped in the soil. This approach importantly produced the same amount of crops as conventional methods. That’s necessary, because converting pasture to arable land to make up crop shortfalls seen with other methods releases large amounts of greenhouse gas. “The need for emissions reductions should be viewed against demands on agriculture, which are increasing as the population and consumption increases and farmers diversify into industrial and fuel crops,” Rob said.

Warming brings home the value of a meal

The 2012 Plant Hardiness Zone Map unveiled by the US Department of Agriculture this year shows average annual extreme minimum temperatures based on data from 1976-2005. In this version 2012 is modified to use the same colour code as 1990. Much of the US was one 5°F (2.8°C) half-zone colder in the 1990 Plant Hardiness Zone Map compared to the latest version. Credit: US Department of Agriculture/Friend of the Earth

Part one of two

Over the past few days I’ve been lucky enough to enjoy the kind of celebrations that would have been called feasting in the past. They’ve brought home how important food is as basic fuel, a source of pleasure and a reason for friends and family to get together. This year, that importance has drawn me increasingly to research into what climate change means for our food supply. What I’ve covered only begins to scrape the surface of the effects we can expect. However, these studies highlight how life could become yet harder for farmers, and what that could cost us all.

The warming world has already noticeably changed plant growing conditions, for example shifting the regions they are suited to grow in the US. In January, the US Department of Agriculture (USDA) redrew its map of planting zones to reflect warming seen since the 1990 version. Partly due to climate change, and partly due to new technology and better weather data, many places are now one 5°F (2.8°C) half-zone warmer. At around the same time, Chinese researchers found that the phases in the seasonal cycle of crop growth in their country had shifted between 1960 and 2008. Springtime events are now 6-15 days earlier and Autumn events 5-6 days later, they found.

2012’s record events put climate in mind

Extent of surface melt over Greenland’s ice sheet on July 8 (left) and July 12 (right). Measurements from three satellites showed that on July 8, about 40 percent of the ice sheet had undergone thawing at or near the surface. In just a few days, the melting had dramatically accelerated and an estimated 97 percent of the ice sheet surface had thawed by July 12. In the image, the areas classified as “probable melt” (light pink) correspond to those sites where at least one satellite detected surface melting. The areas classified as “melt” (dark pink) correspond to sites where two or three satellites detected surface melting. The satellites are measuring different physical properties at different scales and are passing over Greenland at different times. As a whole, they provide a picture of an extreme melt event about which scientists are very confident. Credit: Nicolo E. DiGirolamo, SSAI/NASA GSFC, and Jesse Allen, NASA Earth Observatory

This has been another year of striking climate events and records – but they seem to be happening so much more often today that their effect on me has weakened. That’s pretty cold-hearted, I admit. ‘Extreme weather’ is having terrible effects on peoples’ lives all around the world. But the truth is that we can only handle so many problems before becoming too numbed and overwhelmed to act. And last year, Stefan Rahmstorf and coworkers at the Potsdam Institute for Climate Impact Research showed temperature records are much more likely today than in a stable climate. “I don’t think many people appreciate how much the odds for such extremes have increased due to global warming,” he told me at the time. “I certainly didn’t until we had performed this study.” So it’s hardly surprising if we begin to get complacent when records are flowing thick and fast. But when I actually faced up to what’s happened in the climate this year, it was intriguing how well you could see global warming’s fingerprint.

Warming’s most dramatic effects have long been obvious in the Arctic, and 2012 was no different. Images from three satellites showed that almost Greenland’s entire ice sheet surface was temporarily melted by July 12. That’s the largest area in over 30 years of satellite observations. Then, on September 16, sea ice in the Arctic reached a record annual minimum area of 1.32 million square miles, approximately half the size of the average annual minimum for 1979 to 2000. Just two weeks later, Antarctic sea ice covered its highest area on record at the peak of winter, at 7.49 million square miles. In case you think that’s a natural balance that shows the planet isn’t warming, it’s worth noticing the scale of the changes. The Antarctic record is 193,000 square miles higher than its average maximum area for the last 30 years. That’s much less than the 1.32 million square miles the Arctic lost compared to its long-term average.

Climate provides weak power to predict African violence

Two boys from the Local Defence Unit (LDU) in Kitgum, Northern Uganda, whose job is to protect the people at a refugee camp from attacks and kidnappings by the Lord’s Resistance Army, which has been responsible for much violence in East Africa in recent years. Credit: John & Mel Kots/Flickr

Rainfall and temperature changes are linked to conflict in East Africa, but have less power to predict violence than links to political, economic and geographical factors. That’s according to one of the most detailed studies into climate-violence relationships yet, done by John O’Loughlin from the University of Colorado, Boulder, and his team-mates. “Fears of climate wars across Africa are exaggerated,” John told me. “Any effect of climate change will likely be localized and subject to other conditions.”

One political argument made about our changing climate is that it will bring more violence, particularly in Africa. For example, in 2009, US President Barack Obama told the United Nations that a warming world represents an “urgent, serious, and growing threat” because “more frequent drought and crop failures breed hunger and conflict”. But, with a background of looking in detail at where violence happens and having studied African conflicts before the 1990s, John was concerned that the evidence didn’t back such statements. That’s even though other researchers have reported statistical links between climate and conflict. “I believe that previous studies were limited by data problems and also that the policy discussions were not connected to the research findings,” John explained.

John’s team described how they fixed this in a paper published in the research journal Proceedings of the National Academy of Sciences of the USA on Monday. Previous attempts to study climate-violence have either lacked detail, looking at data per country, per year, or have been too narrowly focussed to allow generalisations, they wrote. John added that this type of work needs detailed data on both conflicts and all the factors that might predict it. Collecting the information needed on conflicts as well as political, health, location and other possibly predictive data was the biggest challenge in the work, he said.

Could pollution be stopping warming’s impact on rain?

A brown cloud of pollution over Phoenix, Arizona. Brown clouds of aerosol pollutant particles could be overwhelming the expected changes in rainfall arising from increasing greenhouse gas levels in the air. Credit: Flick/Flickr

Contrary to previous predictions and measurements, rain patterns have got more uniform as the world has warmed over the past 70 years. So say Michael Roderick and his teammates from Australian National University, Canberra, who’ve developed an ‘accounting system’ that looks closely at where and when rain fell. And the reason could be aerosols – clouds of pollutant particles – produced by humans. “The existing dogma is that increasing greenhouse gas concentrations in the atmosphere have raised rainfall variability,” Michael told me. “In that context, our results emphasise the importance of taking a whole system approach in trying to understand how something complex, like rainfall, is changing in different places.”

When scientists want to understand how climate has been changing over large areas, they usually look at maps of long-term average data that ignore patterns of change in time, Michael explained. When they want to look at how it’s changed over time, they usually either look at a single place or a worldwide average, which ignores patterns in where the changes are. But Michael, along with fellow scientists Fubao Sun and Graham Farquhar, wanted to find a way to link place and time.

To do this Fubao started from a common statistical test called Analysis of Variance or ANOVA. Normally it’s used to compare the effect of different “treatments” – such as a variety of temperatures – on the yield of a crop, for example. In such cases each treatment must be repeated more than once, giving different “replicates”, for the test to be valid. ANOVA can be used to give a value for variance – a measure that shows how spread out an experiment’s measurements are.

Finding nature’s part in Arctic ice loss puts spotlight on human role

University of Reading's Jonny Day talks about his studies into what's contributed to Arctic ice loss

The area of the Arctic covered by ice is set to reach a record low this year* – and much of the ongoing decline is down to man-made global warming. That’s what recent research into the role of three potential natural causes of change in ice coverage done by Jonny Day from the University of Reading, UK, and his colleagues suggests. In a paper published online in scientific journal Environmental Research Letters last month, they studied these three existing sea and wind movement patterns in five different climate models. They found that one in particular, the Atlantic multi-decadal oscillation (AMO), could be responsible for between one-twentieth and three-tenths of the decline in sea ice since the 1970s. “Our work suggests that the AMO has contributed to getting us to this low sea ice state, but does not tell the whole story,” Jonny told Simple Climate. “It is still likely that man-made global warming is the major contributor to the dramatic decline in sea ice.”

Arctic sea ice loss has surprised researchers, as it’s faster than predicted by leading climate models gathered together by the UN Intergovernmental Panel on Climate Change (IPCC). That made Jonny and his co-workers from the Yokohama Institute for Earth Sciences and University of Tokyo in Japan want to look at why this was. In particular, they wanted to see how much might be down to hard-to-predict ‘internal’ climate patterns, rather than problems with measurements of the ice or models. “The large mismatch between climate model projections of sea ice and observations in the last IPCC report was concerning,” Jonny said “My colleagues and I thought that internal or ‘natural’ climate variability may play a role.”

The possible sources of that natural variability include the Arctic Oscillation (AO), which varies between stronger and weaker winds circulating the Arctic. The other two sources come from the ocean, where the AMO is a long-term cycle of temperature change. The final source, the Atlantic meridional overturning circulation (AMOC), is a large-scale ocean flow pattern that carries warm upper waters north and returns cold, deep water south. But a limited set of measurements available for the AMO and AMOC poses researchers a problem. “The oceanic causes of variability we discuss are not well observed, making such analysis difficult,” Jonny said.

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.