Detailed regional data reduce warming-drought link doubts

Sergio Vicente-Serrano and his team have shown that warming is driving more severe and widespread droughts on the Iberian Peninsula, even in this river plain landscape near Aguilar de Campoo in northern Spain Image Credit: tracX via Flickr Creative Commons license

Sergio Vicente-Serrano and his team have shown that warming is driving more severe and widespread droughts on the Iberian Peninsula, even in this river plain landscape near Aguilar de Campoo in northern Spain Image copyright: tracX, used via Flickr Creative Commons license

Spanish and Portuguese researchers have produced some of the strongest evidence yet that warming climate is making droughts more severe. Sergio Vicente-Serrano from the Pyrenean Institute of Ecology (IPE) in Zaragoza and his colleagues have used detailed data from their countries to overcome uncertainties seen in worldwide studies. They have shown that a local warming of 1.5°C from 1961-2011, and 2.1°C in summer months, and rainfall that has decreased by around a sixth increased drought severity in the region. “Future scenarios in the Iberian Peninsula and southern Europe indicate an increase of temperature even more than 3°C for the 21st century,” Sergio told me. “If we have already observed an important decrease of water resources, you can imagine that in the future water resources in these regions will be at higher risk.”

Air holds and ‘demands’ more water as it gets warmer, which is a fundamental reason for why we might expect both worse droughts and heavier rainfall with climate change. Scientists have already used real-world measurements to look at global changes in drought severity. However, they have disagreed on whether things really have got worse in recent years or not. Sergio stressed that such worldwide research faces important limitations. He emphasised that evapotranspiration – the water released by Earth’s surface and by plants breathing – is important in drought studies. But it has to be worked out from a combination of direct measurements, and the records needed are patchy in areas like Africa or South America.

“I’m very critical of the conclusions of these kinds of global studies, not about the methodology, but the input data,” Sergio said. “The problem is the use of highly uncertain variables. There are problems with precipitation data sets in terms of density of observations. The problems for precipitation are much higher for variables that are necessary to estimate the water demand of the atmosphere. Estimating these kinds of variables with confidence is really difficult. Also, there’s no validation in terms of impact on crop production, stream flows, reservoirs, soil moisture, this information is not available. That’s really the approach that must be followed to determine if drought is increasing in severity and impact.” Read the rest of this entry »

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Weather extremes take twin crop and disease toll

Using MODIS data of red and infra-red emissions from the Earth's surface Assaf Anyamba and his colleagues can track conditions including temperature and levels of plant growth. In this shot the Normalized Difference Vegetation Index (NDVI) for southeast Australia from September to November 2010 shows that plants were thriving after a bout of extremely cool, wet weather. Image copyright: PLOSone, used via Creative Commons license, see reference below.

Using MODIS data of red and infra-red emissions from the Earth’s surface Assaf Anyamba and his colleagues can track conditions including temperature and levels of plant growth. In this shot the Normalized Difference Vegetation Index (NDVI) for southeast Australia from September to November 2010 shows that plants were thriving after a bout of extremely cool, wet weather. Image copyright: PLOSone, used via Creative Commons license, see reference below.

The wet and dry weather extremes the world felt between 2010 and 2012 caused wild variations in farm output and encouraged serious diseases spread by insects like mosquitoes. That’s according to scientists from NASA and the US Department of Agriculture (USDA) who studied severe droughts and rainfall that happened in six places during this period. Harvests in the four drought-stricken regions fell to as little as one-fifth of normal levels, but grew dramatically in the two rain-soaked areas, almost doubling in one case. But wet or dry, extreme conditions favoured certain species of mosquitoes (also known as vectors) that went on to cause outbreaks of illnesses like the potentially-fatal Rift Valley Fever. “Extreme weather events can have both negative and positive impacts,” observed NASA’s Assaf Anyamba. “For example eastern Australia and South Africa had bumper harvests of some crops but at the same time had outbreaks of vector-borne disease.”

Assaf and his coworkers help provide ways for the US government to closely monitor the whole world to see where droughts or wet periods might be happening. One way Assaf does this is with a pair of ‘eyes in the sky’ – NASA’s Terra and Aqua satellites. Each carries a Moderate Resolution Imaging Spectroradiometer, or MODIS, which precisely records the colours of the Earth’s atmosphere and surface, including those we can see and reaching far beyond. Scientists use the infra-red data it collects to track surface temperatures, while a combination of red and infra-red can tell them how leafy places are. From these, NASA makes this awesome ‘NDVI’ map of how well vegetated crop-growing regions across the world are, while the USDA includes them in monthly Rift Valley Fever risk reports.

While it’s important to know the impacts of extreme weather, not all countries are able to measure them. But from 2010 to 2012, the MODIS records captured the most intense set of weather they had recorded since Terra’s launch in 1999. The US, Russia, east Africa and southwest Australia endured droughts, and rain drenched South Africa and southeast Australia. Assaf and his team noticed that this weather was influencing both farming and disease in these cases, and decided to look at ‘the big picture’. “We wanted to showcase this connectedness as an example of the mixed bag of impacts anomalous weather conditions impose on society at large,” he explained. Read the rest of this entry »

The climate challenges that my morning toast poses

Britain's wheatfields could become even more productive as the world warms - but that will have implications for further greenhouse gas emissions and fairness to countries less well positioned. Image credit: Tim Gage used via Flickr Creative Commons license

Britain’s wheatfields could become even more productive as the world warms – but that will have implications for further greenhouse gas emissions and fairness to countries less well positioned. Image credit: Tim Gage used via Flickr Creative Commons license

It may seem that nothing could be simpler than toast, but next time I see a slice pop up I’ll also see an emblem of the world’s future. That’s thanks to a UK study exploring the problems surrounding growing enough wheat for flour and other foods as the world warms and has ever more people in it. The issue is especially tangled, Mirjam Röder and her University of Manchester teammates show, as adapting farming for the future will likely increase greenhouse gas emissions, driving further warming. “Climate change and food security are two issues which can’t be decoupled,” Mirjam told me. “The same applies for mitigation and adaptation.”

Mirjam is part of the “Climate change mitigation and adaptation in the UK food system” project, led by Alice Bows-Larkin and backed by Manchester’s Sustainable Consumption Institute. One concern the project reflects is that without adaptation farming will probably be the industry worst hit by climate change, with worldwide productivity falling as temperatures rise. Meanwhile, farming also releases about one-tenth of the greenhouse gases we humans emit overall. “These are largely emissions other than CO2, such as nitrous oxide and methane, mainly occurring from natural processes,” Mirjam said. “They are much harder to reduce and control. Then of course global society is challenged by increasing global food demand. So we face a triad of challenges in the food system: we need to reduce emissions, while food demand is increasing and the sector is impacted by climate change.”

Alice and Mirjam’s team looked at wheat because it makes up almost a third of all cereals grown in the world. “Global wheat demand is projected to increase by about 30% by 2050,” Mirjam. “If we don’t find methods to reduce them, total emissions from producing more wheat will rise.” As well as gases released directly by bacteria and other soil microorganisms, emissions from wheat farming arise from the energy needed to produce nitrogen fertiliser. Whether growing more wheat or dealing with rising temperatures, farmers will need more fertiliser, driving more emissions and therefore further warming. Read the rest of this entry »

Is our weird weather linked to climate change? Oddly, sport can show us the score.

UK Met Office data shows some parts of the country had more than three times average rainfall levels in January, and the country overall set a new rainfall record for the month. Contains public sector information licensed under the Open Government Licence v1.0

UK Met Office data shows some parts of the country had more than three times average rainfall levels in January, and the country overall set a new rainfall record for the month. Contains public sector information licensed under the Open Government Licence v1.0

In a sane world, the worldwide weather chaos that has engulfed the start of 2014 would be memorable. As the eastern US and Canada freeze in winter storms of ‘historical proportions’ as far south as Texas, California remains parched and record temperatures have baked Alaska. As increasingly regular heatwaves scorch Australia, the UK is drowning under record rainfall and being battered by hurricane-force winds, with storms also felt elsewhere in Europe. Yet we may soon forget these dramas and have our attentions sucked in by a new set of meteorological monsters, if they’re linked to changing climate. But are they? Though it’s a murky question, if you look at it like sport, it’s easier to get a feel for than you might think.

Even if you detest football (or soccer, if you prefer), you’ll likely know that in sport the metaphorical playing field is often uneven. Take, for example, last Saturday’s English Premier League match between Manchester City and Norwich City. The Manchester side is owned by Sheikh Mansour bin Zayed Al Nahyan, whose personal wealth is estimated at £20 billion, lavished happily on players for his club. The joint majority owner of the Norwich side is celebrity chef Delia Smith who, despite her success, doesn’t quite have Sheikh Mansour’s financial muscle.

The status difference can be seen in Manchester City’s current lofty league position, and Norwich’s place near the foot of the table. It was obvious last November, when Manchester City thumped Norwich 7-0. So even though last weekend’s match was in Norwich, bookmakers knew Manchester City’s chances of winning were good. Their odds rated a Manchester City win as nearly eight times as likely as a Norwich win, and nearly four times as likely as a draw. But with the unpredictability that gives sport its excitement, Norwich battled hard and kept their opponents from scoring, earning themselves a 0-0 draw. Read the rest of this entry »

Heat drives Pakistani migration

Shahdadpur, Sanghar district, Pakistan: Residents collecting their belongings on a higher ground outside village during floods. Though they may be displaced temporarily, Valerie Mueller from the International Food Policy Research Institute (IFPRI) in Washington DC and her team find high temperatures are more likely to drive permanent migration. Image credit: Oxfam International

Shahdadpur, Sanghar district, Pakistan: Residents collecting their belongings on a higher ground outside village during floods. Though they may be displaced temporarily, Valerie Mueller from the International Food Policy Research Institute (IFPRI) in Washington DC and her team find high temperatures are more likely to drive permanent migration. Image credit: Oxfam International

Excessive rainfall rarely drives Pakistanis to permanently leave their villages, even when it causes hardship like the flooding that hit around a fifth of the country in 2010. Yet they do consistently move in response to extreme temperatures, Valerie Mueller from the International Food Policy Research Institute (IFPRI) in Washington DC and her colleagues have found. She says the finding is a first stage in establishing if, how, and why people’s choices are affected by climate and climate change. “This is a useful step in order to be able to predict migration flows and inform local governments how might they better prepare in terms of the delivery of resources and investing in infrastructure given the occurrence of extreme weather events,” she told me.

There are few efforts collecting information about who has migrated and why over long periods of time, especially in areas where extreme weather occurs. But IFPRI has a long history of evaluating questions linked to food security in countries across the world, including Pakistan. From 1986-1991 its Pakistan Rural Household Survey questioned 800 households about how they lived and farmed, and it has tracked those households ever since. “Local collaborators found the original households in 2001 and 2012 and asked the head of household or an otherwise knowledgeable person what happened to each household member who resided with them in 1991,” Valerie said. “Our study is one of the first to quantify long-term migration patterns over a long period of time.”

The follow-ups recorded the long-term movements and fortunes of 4,428 people from 583 households. The researchers combined these answers with temperature and rainfall data in one ‘logit’ and one ‘multinomial logit’ model designed to let them measure the odds that people moved. “The first model allows us to answer: What are the odds of a person moving out of the household in response to extreme temperature or rainfall?” Valerie explained. “The second model allows us to distinguish moves by location and allows us to answer the following questions: What are the odds of a person moving out of the household but within the village in response to extreme temperature or rainfall? What are the odds of a person moving out of the household but out of the village in response to extreme temperature or rainfall?” Read the rest of this entry »

Planners must be alert to CO2 impact on water supplies

The River Exe submerges the end of a pub beer garden by the Miller's Crossing bridge in Exeter. Nigel Arnell from the University of Reading and his team have predicted some increases in high river flow levels as climate change continues, but even larger decreases in low flow levels.

The River Exe submerges the end of a pub beer garden by the Miller’s Crossing bridge in Exeter. Nigel Arnell from the University of Reading and his team have predicted some increases in high river flow levels as climate change continues, but even larger decreases in low flow levels.

Although the river that slices through Exeter, UK, where I live, is today full from weeks of heavy rain there has been little reported harm from flooding. In the past, most notably in 1960, similar downpours swelled the river Exe until it engulfed the surrounding streets – and so we now have a flood defence system. But shifts in rainfall patterns are potentially the most serious climate changes that we’re facing as a result of the CO2 we emit. They pose a particular threat in a nation like China, where many ‘face severe water distress’, and where this month forestry officials warned about the country’s shrinking wetlands. Drought or deluge, what we do about climate change could have big effects on water supplies.

UK planners already include climate change in their water resource schemes, the University of Reading’s Nigel Arnell told me. But Nigel and his colleagues have also shown they’ll still need to be watchful if we stick to the non-binding Copenhagen Accord on climate change. “We can’t assume that if we adopt a stringent climate mitigation policy then we don’t have to worry about potential effects of climate change on water resource availability over the next few decades,” he told me. “This isn’t actually a surprise, because we know that impacts will continue even if we manage to hit a 2°C target.” Read the rest of this entry »

Give those we love the climate they deserve

Residents in Azaz, Syria on 16 August 2012 clear up after their buildings were bombed during the country's civil war, for which one of the many causes was a drought that has been linked to climate change.

Residents in Azaz, Syria on 16 August 2012 clear up after their buildings were bombed during the country’s civil war, for which one of the many causes was a drought that has been linked to climate change.

Over the next week I hope to be spending time with those I love the most. But this week I’ve been reading the latest newsletter from Medecins Sans Frontiers/Doctors Without Borders (MSF) about the horrible situation in Syria. The country’s civil war has been ongoing since 2011, with a toll that puts the good fortune me and my family enjoy into chilling context.

It’s estimated that there have been 120,000 deaths with over 4.5 million – in a country of just 22.5 million – having to leave their homes. Though that’s a lot of people, I am increasingly numb to the numbers, like many of you might be. But the stories from MSF really hit home. Yes, Syria had serious problems before the war, but it had a comparatively good health system. Now, if you have asthma, diabetes, or appendicitis, it can be life threatening. Ever more children are being born with severe defects, possibly due to the mothers not getting enough folic acid in their diet.

Though there are many factors behind the conflict, an important one is a drought that hit the country’s poorest areas in early 2011. Commentators have highlighted that droughts in Syria have become more common in recent years, linking this to climate change. Earlier this month, US scientists reported that a recent three year drought in Syria was too unusual to be a natural event. All of us who use fossil fuel energy likely bear some responsibility.

While it’s always hard to be certain about such links, they’re backed up by what University of California, Berkeley’s Ted Miguel told me in August. “Many global climate models project global temperature increases of at least 2°C over the next half century,” Ted told me. “Our findings suggest that global temperature rise of 2°C could increase the rate of intergroup conflicts, such as civil wars, by over 50% in many parts of the world, especially in tropical regions where such conflicts are most common.”

Earlier this month, Jim Hansen from Columbia University in New York and his team warned that even world average temperatures 1°C above pre-industrial levels would be dangerous. The Earth has already warmed 0.8°C in the past 100 years, meaning that threshold is near. And many other researchers I’ve spoken to this year have found evidence that shows the dangers. Read the rest of this entry »