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If we are trying to keep global warming to 2 degrees Celsius or less but 4 degrees is possible even within some of our lifetimes, which world do we prepare for? Talks at today's session on adaptation took on the problem of the multiple futures that decision-makers have to face. Mark Stafford-Smith of CSIRO in Australia talked specifically about long-term decisions - such as planting and managing forests - where the best option depends on which way the climate goes later this century. If you expect strong mitigation that holds down warming, then you try to preserve today's forests and nurse them through, protecting them from fire and other threats. If a moderately high temperature is in store, forest composition will have to change and you can plant new species to facilitate that. With runaway climate change the best option could be opening up the forests to invading weeds and rapid, radical transformation.

This is no hypothetical choice. During February's raging wildfires in southeastern Australia, it appears that even the seed stores in the forest floor were destroyed in some burnt areas. Stafford-Smith recommends that conservation managers trying to bring these areas back to life should divide their efforts to follow all three approaches above. Such a hedging strategy may mean two-thirds of forest plans need to be abandoned and altered as the future unfolds, but it's better then putting all the trees in one basket.

Rob Swart of Wageningen University, The Netherlands, looked at hedging on a much larger scale - the plan Bs we could prepare in case of a true planetary emergency. From geoengineering schemes that risk severe side effects to extreme emissions reductions that would affect the climate only slowly and probably require tight government control, none of the options are attractive. But Swart thinks there should be an international process - separate and parallel to current UN climate policy - for countries to work out ahead of time how they would cooperate on such schemes. If left to a moment of panic, they're unlikely to be carried out thoughtfully and equitably.

Anna Barnett

Posted by Anna Barnett on September 30, 2009
Categories: 4 Degrees and Beyond, Adaptation, Anna Barnett, Climate Policy | Permalink | Comments (0) | TrackBacks (0)

Immersing yourself in the impacts of extreme climate change can give rise to a certain amount of gallows humor. Conversation among my dinner companions last night turned to whether this week's 4 Degrees and Beyond conference or March's Copenhagen Climate Congress provided "more apocalypse for your conference fee". The far more serious question, of course, is how much upheaval and human suffering would come with the substantial warming that delegates here are contemplating. Some interesting talks today looked at the facets of sea level rise and population displacement.

Stephan Rahmstorf of the Potsdam Institute for Climate Impacts Research had an intriguing update on a 2007 Science paper in which he'd come up with a new method for projecting sea level rise. Rahmstorf throws out any attempt to use complex climate models on this controversial problem and instead starts from scratch, with observed relationships between temperature rises and sea level rises. Now, working with Martin Vermeer of the University of Technology in Helsinki, he's upgraded the extremely simple equation he used in 2007 to an only slightly less simple equation - one that takes account of the rate of warming and the amount of water that humans sequester in reservoirs. They use this to reconstruct a remarkably faithful record the last millennium's sea levels.

Turning it to IPCC temperature projections, the team finds that sea level rise by 2100 could range, depending on the emissions scenario, from 0.75 to 1.9 metres, and a 4-degree world would likely see 0.98 to 1.3 metres of rise this century. A caveat: the recent sea-rise data that inspired and calibrated this equation and the past data that it explains don't include the full effects of melting ice sheets that could lie ahead. That means 0.75 to 1.9 metres may be a conservative estimate.

But if we're concerned with how creeping seas affect coastal populations, the amount of rise is not the only matter to settle. This was a key argument made by Francois Gemennes of the Institute for Sustainable Development and International Relations in Paris. Gemennes' talk was based on a study of environmentally induced migration that I covered earlier this year. When it comes to climate refugees, he says, the numbers that are often tossed around - such as 200 million new migrants by 2050 - are based on the assumption that greater climate impacts will push more people around. What they aren't based on is empirical data about how populations respond to environmental change. But according to the recent EACH-FOR project - the first global-scale survey of environmental migrants - the size of impacts isn't the crucial variable at all: migration largely depends on policies making it possible for people to react to impacts by migrating. In particular, Gemennes argues, the poorest and most vulnerable will not be able to migrate unless they are given resources and exit routes - if we don't encourage migration as an adaptation strategy, they'll be trapped in the frying pan (or flooding delta).

The next event of the conference is a panel discussion on "4 degrees of climate change: alarmist or realist?", which I'll be tracking over on Twitter. Follow @annabarnett.

Anna Barnett

Posted by Anna Barnett on September 29, 2009
Categories: 4 Degrees and Beyond, Adaptation, Anna Barnett, Ocean science, Society | Permalink | Comments (0) | TrackBacks (0)

Unless major breakthroughs in policy, industry and individual behavior turn around our emissions trajectory pronto, this century could well see average global temperatures 4 degrees Celsius or more above their pre-industrial baseline. That's the starting point for the 4 Degrees and Beyond conference in Oxford this week. Here, 130 scientists and policy experts are taking a detailed look at a world warmed by twice the amount that's usually considered dangerous.

Putting weight behind the 4-degree premise was new modelling research presented this morning by Richard Betts of the UK Hadley Centre (press release, Guardian). Betts's team used a complex, coupled ocean-atmosphere model to simulate the IPCC's extreme-emissions A1FI scenario (the FI stands for fossil fuel intensive) - an emissions trajectory that's previously been run only on simpler models. It's time to take this scenario seriously, argues Betts, given that our emissions are running at the upper end of what the IPCC projected a decade ago.

They also tried out weakening climate sinks on land and sea - feedbacks that are increasingly apparent in recent research, Betts says. Depending on the strength of the feedbacks, 4 degrees of average warming could be reached well before 2100 - as early as 2060 in a worst case scenario, and in the 2070s according to the team's best guess. Regional warming would be far greater, they found - 7 degrees in many areas, up to 10 in western and southern Africa, and 10 or more in the Arctic.

Sessions afterwards started sketching out consequences in detail. Philip Thornton of the University of Edinburgh looked at agriculture in Africa, where projected impacts are predictably devastating, with yields falling over 50% for certain crops and crop failure years growing more frequent in many regions. Adaptations for this amount of change are a big question mark. Intensive agriculture in highlands - among the few spots that will benefit - may be one possibility for preserving the food supply.

Meanwhile in Finland - where you might expect balmier weather to be a boon - intense climate change may also prove a curse to farmers, reports Reimund Rotter of MTT Agrifood Research Finland. The picture there is complicated - the possible responses depend on many variables. A new type of barley that might compensate for losses to rising temperature or drought would only work in certain soil types, for example. But it's clear that the North as well as the South will have its problems with the radically different 4-degree world.

Anna Barnett

Posted by Anna Barnett on September 28, 2009
Categories: 4 Degrees and Beyond, Adaptation, Anna Barnett, Climate Science, Climate prediction, Society | Permalink | Comments (0) | TrackBacks (0)