Climate sensitivity wrangles don’t change the big picture on emissions

The sources of data that scientists can use to determine climate sensitivity include ice cores, the cylinders these researchers are holding at the Vostok station in Antarctica. Image credit: Todd Sowers, Columbia University

The sources of data that scientists can use to determine climate sensitivity include ice cores, the cylinders these researchers are holding at the Vostok station in Antarctica. Image credit: Todd Sowers, Columbia University

How much does the world warm up in response to a certain amount of greenhouse gases like CO2 in the atmosphere? It’s a simple question, but its answer depends on whether you mean short-term or long-term warming, and estimates vary according to the methods used. Scientists are currently intensively debating long-term ‘climate sensitivity’, which begs prompts the question: might we be pushing too hard to cut climate CO2 emissions, if this is uncertain?

The answer is no, according to Joeri Rogelj from the Swiss Federal Institute of Technology, ETH Zurich, and his coworkers. They looked at how a range of climate sensitivity values affected their 21st century warming projections in a paper published in Environmental Research Letters last week. “When taking into account all available evidence, the big picture doesn’t change,” Joeri told me. The ‘carbon budget’ of greenhouse gases we could still emit today and in the future is very limited whatever the climate sensitivity, he explained. “Keeping the so-called carbon budget in line with warming below 2°C still requires a decarbonisation of  global society over the first half of this century.”

Climate sensitivity is the measure of how much the world will eventually warm when it reaches equilibrium after a doubling of CO2 in the air. Today, we have upset the normal equilibrium where the Sun’s energy flowing into the atmosphere matches the flow the Earth radiates back out of it. Now more is coming in than leaving, and that’s heating the planet up. Think of the atmosphere as a series of pipes, with energy flowing through them like a liquid. The Earth is a reservoir in the system, filled by an incoming pipe and drained by an outgoing one. CO2 acts like a blockage in the outgoing pipe – it slows the outward energy flow and causes a build-up in the reservoir. When the reservoir gets fuller it can put enough pressure on the blockage for the outward flow through it to again match the incoming flow. Then we’d be at equilibrium, but with a fuller reservoir – a warmer planet. The more CO2 we emit, the worse the blockage gets and the hotter we get before reaching equilibrium. Read the rest of this entry »

Fairness instinct trumps economic expectations on climate costs

ETH Zurich's Robert Gampfer hopes governments can learn from the climate negotiation games he ran. Image credit: ETH Zurich

ETH Zurich’s Robert Gampfer hopes governments can learn from the climate negotiation games he ran. Image credit: ETH Zurich

We care about fairness in sharing climate change costs, although differences in who’s more vulnerable to it can affect our ideas of what exactly is fair. That’s the clear suggestion emerging from a set of climate change negotiation games run by Robert Gampfer from the Swiss Federal Institute of Technology, ETH Zurich. In his experiments, students from Zurich universities took on the role of countries in climate talks trying to agree how costs should be shared. Robert feels this unusual approach provides unique insights into our true attitudes, and could help guide our leaders in responding to them.

“Proposals that are perceived as very unfair are likely to meet public resistance, and governments will therefore be unlikely to agree to them in the international negotiations,” he told me. “But the experiment also showed that participants who were richer or more responsible for climate change often acted rather fairly, even if this meant higher costs for them. This is quite a far-reaching conclusion, but maybe governments of developed countries could actually sell costly climate agreements to their citizens if they perceive some fairness obligation to accept them.”

This study builds on a realisation Robert made when looking into possible topics for his climate politics PhD, which he’s now writing the final thesis for. “A lot of surveys on climate change and climate policies ask only very broad questions – whether you would support your country reducing its emissions or not, for example,” he observed. “But we know very little about how specific aspects of global climate politics influence people’s opinion, for example the debate on burden-sharing fairness. In a standard survey it is easy to be in favour of emission reductions, because stating this does not cost you anything. Real emission reductions probably would have some cost, for example through higher energy prices.”

In seeking deeper insights, Robert realised that political science and economic experiments hadn’t addressed fairness much either. “This might be because many think people’s fairness preferences are not important for an international climate agreement,” he said. “I find this quite surprising: in the negotiations, governments use fairness arguments very often. And they probably do this, among other reasons, because they will receive domestic support from their citizens for adopting such negotiating positions.” 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 »

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 »

Renewable energy beats ‘clean coal’ on cost in Australia

A part of the extension of the Snowtown Wind Farm in South Australia that added 90 new 3 megawatt turbines. In South Australia wind farms contribute 27% of annual electricity, notes University of New South Wales' Mark Diesendorf. Photo by David Clarke, used via Flickr Creative Commons license.

A part of the extension of the Snowtown Wind Farm in South Australia that added 90 new 3 megawatt turbines. In South Australia wind farms contribute 27% of annual electricity, notes University of New South Wales’ Mark Diesendorf. Photo by David Clarke, used via Flickr Creative Commons license.

It’s unlikely that fossil fuel power stations that capture and store their CO2 emissions could supply eastern Australia’s electricity more cheaply than renewable energy technologies like solar and wind power. That’s according to a study based on hour-by-hour analysis of electricity demand by Ben Elliston, Iain MacGill and Mark Diesendorf from the University of New South Wales in Sydney. Although renewables are often seen as expensive, these findings highlight that they can be competitive after accounting for the impact of burning coal and gas on our climate. “Our studies, and those conducted by other research groups around the world, find that it is possible to operate reliable national and subnational electricity systems on predominantly renewable energy generated by commercially available technologies and that these systems are affordable,” Mark told me.

Ben is a PhD student, supervised by Iain and Mark, and together the three have sought to answer key questions about renewable energy. Is it possible to supply a whole electricity grid’s needs with these technologies, or are some ‘base-load’ coal or gas power stations needed to fall back on? And if it is possible, would it be affordable?

To answer these questions, Ben designed a computer programme to simulate running an electricity supply system. His program can go through a year’s hourly data on electricity demands, wind and sunshine over the region in a fraction of a second. “Everything else follows from this, provided of course one asks the right questions,” Mark noted.

Over the last two years they have published work exploiting that programme, first showing that it’s possible to reliably supply 100% of eastern Australia’s electricity using renewable energy. Wind and solar power supplied most of the electricity, but output from these technologies varies due to changes in weather. But rather than filling gaps with fossil fuels, they showed existing hydroelectric power stations and gas turbines burning biofuels could be used to meet the grid’s reliability standard. Read the rest of this entry »