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 »

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 »

Real-world grounding could cool 21st century outlook

The world's surface air temperature change ("anomaly"), relative to the world's mean temperature of 58° F or 14.5° C, averaged over land and oceans from 1975 to 2008. Inset are two periods of no warming or cooling within this overall warming trend. Copyright 2009 American Geophysical Union. Reproduced/modified by permission of American Geophysical Union.

The world’s surface air temperature change (“anomaly”), relative to the world’s mean temperature of 58° F or 14.5° C, averaged over land and oceans from 1975 to 2008. Inset are two periods of no warming or cooling within this overall warming trend. Copyright 2009 American Geophysical Union. Reproduced/modified by permission of Wiley/American Geophysical Union, see citation below.

Starting climate models from measured data helps simulate the early-2000s global warming hiatus better, and reduces projections for warming through to 2035. Jerry Meehl and Haiyan Teng have compared such ‘initialised’ model runs against more common ‘uninitialised’ ones starting without real-life conditions. The scientists, from the US National Centre for Atmospheric Research (NCAR) in Boulder, Colorado, find initialised runs get closer to modelling that hiatus and surprisingly rapid warming in the 1970s. Using the same approach, admittedly rough 30-year predictions for Earth’s surface air temperature initialised in 2006 are about one-sixth less than uninitialised projections. “We have evidence that if we would have had this methodology in the 1990s, we could have predicted the early-2000s hiatus,” Jerry told me.

The hiatus Jerry and Haiyan studied – an easing off in the rate of global warming since 1998 – is perhaps the aspect of climate change most hotly debated today. But hiatus is a slippery word, whose meaning depends on who is highlighting what points on which graph. Climate skeptics will often infer that it’s evidence that global warming is not a problem, or that it shows we know too little to act on climate change. The UN Intergovernmental Panel on Climate Change puts it in plain numbers: the rate of warming from 1998-2012 was 0.05°C per decade; from 1951 to 2012, it was 0.12°C per decade. “In addition to robust multi-decadal warming, global mean surface temperature exhibits substantial decadal and interannual variability,” it adds.  “Due to natural variability, trends based on short records are very sensitive to the beginning and end dates and do not in general reflect long-term climate trends.”

In a paper published online in the journal Geophysical Research Letters last week, Jerry and Haiyan touch on the current best explanations of the let-up. These include the chilling effect of recent volcano eruptions, but mostly focus on cooling in the Pacific as part of a natural cycle. Called the Interdecadal Pacific Oscillation (IPO), this regular wobble in sea surface temperatures has likely partly masked greenhouse-gas driven warming. The IPO has also been linked to a larger warming than might have been expected from greenhouse gases alone in the 1970s, the NCAR researchers add. Read the rest of this entry »

Climate change science anyone can play with

It’s all very well to read about climate change – but you can probably get a better understanding from actually exploring the data and underlying physics yourself. That’s been driven home by some recent comments on this blog by non-scientist readers wanting to do just this, or recommending that I do. Inspired by them, in this week’s blog entry I’m bringing together various different ways we can all do this. Don’t worry, I won’t tax any weary brain cells any more than they want to be. I’m organising the blog entry in order of increasing effort/difficulty – just bail out or take a break whenever you need to.

The volume occupied by the average yearly CO2 emitted by someone in the UK is as big as a building. Credit: Carbon Quilt

The volume occupied by the average yearly CO2 emitted by someone in the UK is as big as a building. Credit: Carbon Quilt

As a simple starter, try the Carbon Quilt tool that lets you see your CO2 emissions. If you click on this link or the image above you should first see the size of a ‘quilt’ or ‘patch’. That represents the average amount of CO2 people in your country emit, overlaid on a map. Try out the sphere and cube options, and the different options in the drop-down menu to see how big your carbon footprint really is.

Click here to see how hot the Earth's predicted to get in your lifetime, and the lifetimes of children born today. Credit: The Guardian

Click here to see how hot the Earth’s predicted to get in your lifetime, and the lifetimes of children born today. Credit: The Guardian

Another simple but powerful demonstration is the Guardian interactive guide to how warm it will get in our lifetimes pictured above.

Click here to see how unusual current CO2 levels are, and how much worse they're set to get. Credit: The Guardian

Click here to see how unusual current CO2 levels are, and how much worse they’re set to get. Credit: The Guardian

Still more powerful, I think, is this guide showing the significance of CO2 levels in the air hitting 400 parts per million last year. 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 »

Warming makes flowers change dates, or don skates

Blue Fleabane (Erigeron acer) has only moved its flowering date forward around by 3 days in 50 years, and instead the places where it's found in the UK have moved north by around 9 miles. Image credit: Vlad Proklov, used via Flickr Creative Commons licence.

Blue Fleabane (Erigeron acer) has only moved its flowering date forward around by 3 days in 50 years, and instead the places where it’s found in the UK have moved north by around 9 miles. Image credit: Vlad Proklov, used via Flickr Creative Commons licence.

If plants can’t flower earlier to adapt to global warming they’re probably being driven away from where they used to grow, towards cooler places. That’s what new findings on how these responses are linked from Tatsuya Amano at the University of Cambridge and his teammates suggest. “We believe that the link we’ve revealed will help us understand the complex implications of climate change on biodiversity,” Tatsuya told me. “Many studies have relied on models that only consider species’ spatial responses for projecting the impact of climate change on species. We might be able to generate more realistic projections.”

You could think of regular natural events, such as flowering in plants, as being triggered by an alarm clock – another type of dandelion clock, if you like. The study of when those alarms go off is known as phenology. In 2009, Tim Sparks from Coventry University visited Tatsuya, Bill Sutherland and others in Cambridge to give a talk on changes in when these events were happening. He was helped by notes on plant life many people in the UK had jotted down in their spare time, but that data’s inevitable patchiness caused him problems.

Bill and Tatsuya were working on mathematical models that helped fix similar problems in bird count data, and so they offered to help Tim with his work. They were also joined by Richard Smithers, then in charge of the Nature’s Calendar archive run by the UK’s Woodland Trust. He helped them realise the power of this publicly-accessible record of over 250 years’ worth of data on 405 UK species, nearly 400,000 records in all. Using that information, in 2010 the team showed that UK flowers are now blooming earlier in the year than in any 25-year period since 1760.

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 »

The man who got the world to agree on climate

  • This is part two of a two-part post. Read part one here.
When not tackling climate science or negotiations Bert Bolin liked nothing more than a little choir singing. Credit: KVA

When not tackling climate science or negotiations Bert Bolin liked nothing more than a little choir singing. Credit: KVA

In 1975, advised by Bert Bolin, the Swedish government drafted a bill on future energy policy containing a conclusion that elsewhere might be controversial even today. “It is likely that climatic concerns will limit the burning of fossil fuels rather than the size of the natural resources,” it foresaw. Produced thanks to Bert’s early role tackling environmental issues, it was one of the first times humans’ effect on climate and the risk it poses us was noted officially. For more than two decades afterward the Stockholm University researcher would further strengthen that case, both through his research and by putting climate science firmly on the political agenda. And those tireless efforts would help the United Nations’ Intergovernmental Panel on Climate Change (UN IPCC) to consistently achieve what otherwise might have been impossible agreements.

The Swedish bill was a bold statement, given that average air temperatures were only just about to reverse a slight cooling that had gone on since 1940. Bert and scientists like Dave Keeling had shown that CO2 levels in the atmosphere were rising. Basic science established by Svante Arrhenius 80 years before had showed this should warm Earth’s surface. So why was it cooling? The way scientists found the answer was typical of the progress in climate science Bert was overseeing. They would use the latest tools, including computers and satellites, bringing theory and measurement together to improve our understanding.

Climate models in the early 1970s were still simple by today’s standards, but had advanced from the early computerised weather predictions Bert had previously pioneered. And when Columbia University’s Stephen Schneider and S. Ichtiaque Rasool added aerosols of floating dust to CO2 in a model for the first time, they found a possible explanation for the temperature drop. The aerosols, particularly human pollution, created a cooling effect that swamped the warming – so much so they warned it could trigger an ice age. Though Stephen and Ichtiaque soon realised that their model overestimated the cooling, aerosols obviously deserved a closer look.

To clear up such murky problems, the Global Atmospheric Research Programme (GARP) that Bert jointly set up would bring together scientists from around the world, despite the cold war. As GARP’s first experiments, looking at heat and moisture flow between the atmosphere and ocean, started in 1974, Bert organised a meeting in Stockholm on climate physics and modelling. GARP had two goals – improving 6-10 day weather forecasts first, and climate change predictions second. As it gradually became clear how hard the first was, climate forecasting became more important.

Diplomacy was needed among the gathered scientists as arguments flared over how ambitious they should be. Should they strive for satellites that could collect the high resolution data scientists and models needed, even though that was beyond their capabilities at the time? And significantly for later climate work – should they seek to produce results so society could respond to change, even when results were uncertain? Bert was clear on that one: scientists had to answer socially important questions, though he was in a very small minority prepared to say so openly. Read the rest of this entry »

The underprepared figurehead that led climate science from calculation to negotiation

Bert Bolin discussing weather maps in Stockholm circa 1955. Image copyright Tellus B, used via Creative Commons license, see Rodhe paper referenced below.

Bert Bolin discussing weather maps in Stockholm circa 1955. Image copyright Tellus B, used via Creative Commons license, see Rodhe paper referenced below.

In 1957, at the young age of 32 and just one year after completing his PhD, Bert Bolin officially gained a new skill: leadership. Taking over the International Meteorological Institute (IMI) in Stockholm, Sweden, after his mentor Carl-Gustaf Rossby’s sudden death must have been a huge shock. But Bert gained responsibility after responsibility over the next 40 years, ultimately becoming the first chairman of the United Nations’ Intergovernmental Panel on Climate Change (UN IPCC). And though it’s hard to beat setting up a Nobel-prize winning organisation, Bert was not just an administrator – his research helped build the foundations of climate science too.

Growing up in Nyköping, south of Stockholm, Bert recorded the weather with encouragement from a schoolteacher father who had studied meteorology at university. After the pair met the Swedish Meteorological and Hydrological Institute’s deputy director when Bert was 17, he moved north to study maths, physics and meteorology at the University of Uppsala. Immediately after graduating in 1946 he went to Stockholm to do military service, where he first saw Carl-Gustaf giving a series of lectures.

By that time Carl-Gustaf had been living in the US for 21 years, pioneering mathematical and physical analysis of the atmosphere, becoming the country’s foremost meteorologist. He had set up meteorology departments at Massachusetts Institute of Technology in the 1930s, and the University of Chicago, Illinois, in the 1940s. He had also modernised the US Weather bureau and by 1946 wanted to help improve meteorology’s status in his native Sweden. As Carl-Gustaf’s renowned organisational prowess gradually pulled together the IMI, Bert came to study with him, gaining his Master’s degree in 1950.

Carl-Gustaf was collaborating with leading scientists of his time, and through some of these links Bert spent a year working in the US after his Master’s. Perhaps the most notable such relationship was with John von Neumann at Princeton University in New Jersey, who had helped develop the hydrogen bomb. John and his team had made history using arguably the world’s first computer, ENIAC, to predict weather mathematically. But when errors emerged, Carl-Gustaf asked Bert to help analyse why, using his understanding of the atmosphere to prevent such forecasts being ‘mathematical fantasy’. Read the rest of this entry »

Tundra plants show modern temperatures unmatched in over 44,000 years

Gifford Miller collects vegetation samples on Baffin Island. Credit: University of Colorado, Boulder.

Gifford Miller collects vegetation samples on Baffin Island. Credit: University of Colorado, Boulder.

Tiny plants in Arctic Canada have shown that average summer temperatures there over the last 100 years are higher than those during any century for over 44,000 years. Gifford Miller from the University of Colorado, Boulder, and his teammates collected plants perfectly preserved but recently revealed by rapidly retreating ice sheets. The temperature findings are especially surprising as around 10% more energy from the sun fell on the Northern half of the planet 5,000 years ago than today.  And by looking at other scientists’ historical temperature records, they think the last time temperatures were as warm as today was likely around 120,000 years ago. “This adds to the growing consensus that the greenhouse gases we’ve added to the atmosphere have made a very large difference to the planet’s energy balance,” Gifford told me.

Scientists have known receding glaciers on Baffin Island are revealing well-preserved moss and lichen for almost 50 years. Gifford first read about it during his PhD, which he completed in 1975, in a paper written by a Canadian Department of Mines and Technical Surveys employee in 1966. “I had been to that site in 1981, found where he’d built a camp at the ice edge, measured how far the ice had disappeared and found plants coming out,” he recalled. “I’d repeated what he had done, but hadn’t done anything else with it. But as the ice is melting a lot right now we hypothesised that this wasn’t an isolated case.”

Glaciers don’t usually preserve what’s underneath them. “It’s almost counterintuitive to some people – you think of ice doing some damage to the landscape,” Gifford said. “But ice doesn’t move on its own, it’s driven by gravity. Where it’s flat, there’s not a whole lot of gravity pushing it, and if the ice is fairly thin and cold it’s an exquisite preservation agent. They’re frozen solid when they’re under the ice, which is very cold, like -14°C.” Sites like that can be hard to get to, as many are on plateaus high above Baffin Island. “You could mount climbing expeditions and spend a week getting to one site, so really there’s no practical way to get up there, except to have very good weather and a helicopter,” the scientist added. Read the rest of this entry »

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