Could climate’s crop impact catch us with our plants down?

The odds that yields of maize will fall by a tenth over the next 20 years have shortened from 1-in-200 to 1-in-10. Image copyright Raman Sharma, used via Flickr Creative Commons license.

With the next two decades set to see a stronger increase in demand for food than the rest of the 21st century, declining harvests would cause some serious problems. Right now crop yields are growing, but could climate trends cause them to fall by a tenth, say, over the next 10-20 years?

That’s the question David Lobell from Stanford University in California and Claudia Tebaldi from the US National Center for Atmospheric Research in Boulder, Colorado have tried to answer. They find that if the world wasn’t warming, the chance of yields decreasing by a tenth over the next 20 years would be less than 1-in-200. However, climate change has made shrinking yields more likely, shortening the odds to a 1-in-10 chance for maize and a 1-in-20 chance for wheat.

“It was surprising to see how likely it is nowadays for climate trends to significantly cut into yield progress,” David told me. “It is still more likely than not that climate will be a slight drag on progress instead of a major factor. But we can’t rule out a major slowdown, and that means we should probably think through that type of scenario to figure out how to prepare for it.”

Such near-future climate forecasts are unusual, David underlined. “Longer periods allow the signal of climate change to become clearer compared to natural variability,” he explained. “But it may simply be that most of the initial questions about climate change were about the long timescales, to decide about questions related to energy choices and emissions. Now, a lot of questions are related about how to properly adapt to the changes happening now.”

What will happen to crops is central to David’s interests as associate director of Stanford’s Center on Food Security and the Environment. “I often get asked by governments or the private sector if climate change will threaten food supply in the next couple of decades, as if it’s a simple yes or no answer,” the scientist revealed. “This was especially true of a committee I recently served on focused on social stresses from climate change in the near-term. The truth is that over a 10 or 20 year period, it depends largely on how fast things warm, and we can’t predict that very precisely. So the best we can do is put odds on things.”

Climate change-boosted disease could endanger China’s food supply

Wheat ear infected with Fusarium ear blight (FEB), giving the ear a pinkish color. The disease could be set to increase in countries like China and the UK with climate change, Bruce Fitt and his teammates have found, suggesting resistant varieties should be developed. Photo credit: CIMMYT.

As the planet warms, China’s wheat crops will be threatened by more frequent epidemics of ‘fusarium ear blight’ (FEB), scientists in the UK and China have projected. Bruce Fitt from the University of Hertfordshire in Hatfield, UK, and his teammates forecast levels of the disease in the Anhui and Hubei provinces from 2021-2050. Whereas in the worst affected regions in 2001-2010 around one-sixth of all ears were infected, this was the lowest disease level the researchers found in their future scenario. In the worst-hit areas, FEB infected more than a third of all ears. “This has implications for crop breeding because it takes 10-15 years to breed a new cultivar,” Bruce told me. “If you know the disease is going to become more important then you need to get on and start breeding now rather than waiting until the disease hits you.”

Today, over a billion people don’t have enough to eat, and further population growth and climate change are set to put the world’s food supplies under even greater strain. To help ease that pressure, Bruce and other scientists are working to understand and help improve control of crop diseases like FEB. While some crop diseases will worsen in the future, not all will, he stressed. “For example, you might have a disease that is spread by rainsplash in summer and then it’s predicted that there will be far less rainfall in summer,” he explained. “Then you would expect that with climate change the importance of that disease would diminish.” If governments, farmers and seed suppliers know which diseases are likely to get worse, they can prioritise developing strategies to contol them, like breeding disease resistant varieties.

To make useful forecasts for which diseases will worsen, scientists build models that include weather data, how crops grow and how the disease pathogen spreads through the crop. “In this particular instance the wheat is susceptible only at flowering,” Bruce said. “It may be in flower for a few days. If it doesn’t get the pathogen inoculum and the right weather conditions at that time it will not get the disease.” Climate change can both alter flowering times and the chances of warm, wet weather that make infection more likely. When wheat gets infected, even if it can be harvested it is more likely to contain poisonous mycotoxins. “If it’s full of mycotoxins then it can’t be eaten by man or beast, so it’s just wasted,” Bruce added.

Dump fossil fuels for the health of our hearts

Air quality in London on April 3, 2014 fell to a level where it became hard to see normally-visible skyscrapers. Conditions hit a 9/10 risk ranking thanks to a combination of pollution and dust blown in from the Sahara desert. Tackling such pollution could immediately improve people’s health, stresses New York University’s George Thurston. Image copyright David Holt, used via Flickr Creative Commons license.

Sometimes when I blow my nose and – inevitably – look into my handkerchief, I see that my snot is black. It doesn’t happen when I’m at home, in the small English city of Exeter, only when I’m in London. It’s a clear sign of the extra pollution I’m inhaling when I’m in the capital – one backed up by data published last week by Public Health England. Its striking report says that in 2010 73 deaths per thousand in the London borough of Waltham Forest, where my girlfriend’s sister lives, could be put down to grimy air. For Exeter, the figure was just 42 per 1000. Across the whole of England, pollution killed 25,002 people in 2010, or 56 of every 1000 deaths nationwide.

But wherever you live, air pollution will become even more important as the climate changes, while fighting this scourge could also help the world bring global warming under control. “There’s more than enough rationale for controlling emissions based on the health effects and the benefits that we get as a society from getting off of fossil fuels,” New York University’s George Thurston told me. “Those are the benefits that are going to accrue to the people who do the clean-up – locally and immediately, not fifty years from now.”

Public Health England is trying to draw attention to ‘particulate matter’, or dust, less than 2.5 micrometres in diameter, too small to see with our naked eye. You won’t find this ‘PM_2.5’ pollution listed as people’s cause of death – it’s likely to be down as a heart attack or lung cancer. George has run huge studies in the US to help work out exactly how much such dust worsens people’s health. One study for the American Cancer Society followed 1.2 million men and women originally enrolled in 1982. Another, started in 1995, tracked over 500,000 US retirees over the following decade. And he was also a part of a worldwide project that last year showed ‘global particulate matter pollution is a major avoidable risk to the health of humankind’.

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 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.”

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

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.

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

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?”

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.

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.”

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.

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.

Twin rainfall effects strengthen human climate impact case

While existing studies of rainfall changes rely on data collected on land, by switching to satellite data LLNL’s Kate Marvel and Céline Bonfils could include changes in rainfall at sea. Image copyright snoboard1010 used via Flickr Creative Commons license.

The way we humans are affecting the climate is changing rainfall patterns over land and sea, scientists at Lawrence Livermore National Laboratory (LLNL) in California have found. Kate Marvel and Céline Bonfils compared precipitation ‘fingerprints’ in satellite data against what climate models showed would result from actions like adding greenhouse gases to the atmosphere. “Everyone knows that temperatures are rising, but figuring out how that affects other aspects of the climate is tricky,” Kate told me. “We’ve shown that global precipitation is changing in the way climate scientists expect it to. The odds of the observed trends being due to natural climate variability are very low.”

Changes to rain, snow and all the other forms of falling wetness collectively known as precipitation are undeniably important, given their power to bring floods and droughts. Scientists have already shown that, over land, wet areas are getting wetter and dry areas are getting drier. These studies rely on data measured directly on land, reaching back almost a century. The long record gives scientists a lot of data to test, making it easier to tell human influences from the many natural rainfall patterns. Yet Kate and Céline wanted to use satellite data instead. Though these have only been recorded since 1979, each measurement is more reliable, and the satellites also cover the oceans.

“With such a short record, it’s often difficult to identify the ‘signal’ of climate change against the background of completely natural variability,” Kate explained. For example, the wet-gets-wetter, dry-gets-dryer strengthening of the Earth’s water cycle happens because warmer air can hold more water vapour. But that can be caused by the El Niño climate pattern, as well as by increasing greenhouse gases. Our activities can also change how air circulates above the planet, pushing dry regions and storm tracks toward the poles – but so can the La Niña pattern.

Braving African piracy reveals abrupt rainfall shifts

Woods Hole Oceanographic Institution’s Jessica Tierney has patiently produced a record of rainfall in East Africa reaching back 40,000 years, from sediment collected from pirate- and extremist-infested waters. Image copyright: Tom Kleindinst, Woods Hole Oceanographic Institution

Having dodged pirates and extremists, and slogged for two years to interpret the record collected, US scientists have shown how abruptly rainy climates in East Africa come and go. Jessica Tierney puzzled out a rainfall record back to the last ice age from mud collected in one of the last research cruises to brave the Horn of Africa. “The region goes from being pretty humid to very arid in hundreds of years,” Jessica, who works at Woods Hole Oceanographic Institution (WHOI) in Massachusetts, told me. “That’s important because there’s a threshold behaviour in its rainfall. We need to better understand what drives those thresholds, and when we’d expect to be pushed over one, as it has huge implications for predicting drought and famine in the region.”

Long interested in ancient East African climate, Jessica wanted to study the Horn of Africa area, which includes Ethiopia and Somalia, because the climate there is very sensitive and variable. But its dry conditions rule out many options scientists use to build historical records from ice, cave deposits, sediments from lake beds or tree rings. So in 2010, she started working with Peter deMenocal at Lamont-Doherty Earth Observatory in New York, who collected sea bed sediments from the area in April and May 2001.

“We boarded ship in Dar Es Salaam in Tanzania and our cruise was to end in Port Said, in Egypt,” Peter told me. That took the team down the Somali coast and into the Gulf of Aden, where a few months earlier suicide bombers killed 17 sailors aboard the USS Cole. Though the scientists were worried, the captain of their Dutch research ship, R/V Pelagia was vigilant. “He had ordered radio silence, and we actually turned off all our lights on the ship at night, even navigation lights,” Peter recalled. “He had also put in orders for us to train on what to do in case we were boarded.”