A three-day conference on climate science and policy that drew some 2,500 scientists, economists, campaigners, dignitaries, industry representatives and journalists to Copenhagen has wrapped up, and organizers have issued a list of core "messages" that you can see at the bottom of this post. Their bottom line, echoing what many climate scientists have been saying with rising vigor for two decades, is that there is an urgent need to curb emissions of greenhouse gases, and "inaction is inexcusable."

Is this effort, which one organizer described as "a deliberate attempt to influence policy," likely to change things? There are signs, some scientists warned on Thursday, that overheated descriptions of looming dangers coming out of the conference could actually backfire. More on those warnings is below.

The meeting, organized by 10 universities and paid for by a variety of corporate sponsors, was mainly aimed at moving beyond what many participants described as the overly conservative findings of the 2007 report from the Intergovernmental Panel on Climate Change. News coverage of the presentations given at the conference over the last few days described new evidence that the Amazon rain forest was poised to dry up and that sea levels could rise more than twice as much as the intergovernmental climate panel projected.

On Thursday, an e-mail message was distributed to a host of Amazon forest experts and to a journalist by Yadvinder Malhi, an Oxford University biologist who is focused on the Amazon and climate. He questioned the Amazon findings presented at the meeting, and decried the resulting media coverage:
I must say I find it frustrating that the gloomiest take on news gets such a big profile. This is based on one model, and that model has flaws (especially its temperature sensitivity that seems too great (David Galbraith's work), and its rainfall that seems to low (our PNAS paper PDF). The danger is that that such apparent bad news makes all the efforts to conserve the Amazon forests worthless (why bother saving them if they are already doomed?), and encourages disengagement and hopelessness rather than action. If that conclusion was based on solid empirical science then so be it, but when such a story goes out on a pure model study (not yet peer-reviewed) with significant imperfections, it may do a lot of damage in the real world.
A colleague of Dr. Malhi who attended the meeting responded by saying several scientists there were engaged in "damage control." When I ran all of this by a couple of social scientists tracking how climate science is conveyed to the public, they groaned (or the e-mail equivalent).

Daniel Sarewitz at Arizona State University said this was a classic example of how scientists and the media play down complexity in their thirst for powerful framing that catches attention and might drive action. The problem, he and several colleagues said, is that over-reaching can also lead to distrust and further polarization of advocates threatened or empowered by the controversial finding. (This is the "climate porn" concept I wrote about a while back.)

Here is the concluding statement from the conference:
"Climate Change: Global Risks, Challenges & Decisions"
Final Messages

Copenhagen, Denmark - 12 March 2009 - Following a successful International Scientific Congress Climate Change: Global Risks, Challenges & Decisions attended by more than 2,500 delegates from nearly 80 countries, preliminary messages from the findings were delivered by the Congress' Scientific Writing Team. The conclusions will be writing into a full synthesis report to be published in June 2009. The conclusions were handed over to the Danish Prime Minister Mr. Anders Fogh Rasmussen today. The Danish Government will host the UN Climate Change Conference in December 2009 and will hand over the conclusions to the decision makers ahead of the Conference.

The six preliminary key messages are:

Key Message 1: Climatic Trends
Recent observations confirm that, given high rates of observed emissions, the worst-case IPCC scenario trajectories (or even worse) are being realised. For many key parameters, the climate system is already moving beyond the patterns of natural variability within which our society and economy have developed and thrived. These parameters include global mean surface temperature, sea-level rise, ocean and ice sheet dynamics, ocean acidification, and extreme climatic events. There is a significant risk that many of the trends will accelerate, leading to an increasing risk of abrupt or irreversible climatic shifts.

Key Message 2: Social disruption
The research community is providing much more information to support discussions on "dangerous climate change". Recent observations show that societies are highly vulnerable to even modest levels of climate change, with poor nations and communities particularly at risk. Temperature rises above 2 degrees C (*) will be very difficult for contemporary societies to cope with, and will increase the level of climate disruption through the rest of the century. [*This is 2 degrees Celsius, or 3.6 degrees Fahrenheit, above the globe's average temperature around 1850, the organizers say. Translated, that would be about 61.6 degrees Fahrenheit. Today's global average temperature is estimated at around 59 degrees. (This was updated after a couple of comment posters noted my funky conversion effort. Europe set its 2-degree limit from pre-industrial temperatures, making this a complicated calculation, and a source of much ongoing confusion.]

Key Message 3: Long-Term Strategy
Rapid, sustained, and effective mitigation based on coordinated global and regional action is required to avoid "dangerous climate change" regardless of how it is defined. Weaker targets for 2020 increase the risk of crossing tipping points and make the task of meeting 2050 targets more difficult. Delay in initiating effective mitigation actions increases significantly the long-term social and economic costs of both adaptation and mitigation.

Key Message 4: Equity Dimensions
Climate change is having, and will have, strongly differential effects on people within and between countries and regions, on this generation and future generations, and on human societies and the natural world. An effective, well-funded adaptation safety net is required for those people least capable of coping with climate change impacts, and a common but differentiated mitigation strategy is needed to protect the poor and most vulnerable.

Key Message 5: Inaction is Inexcusable
There is no excuse for inaction. We already have many tools and approaches - economic, technological, behavioural, management - to deal effectively with the climate change challenge. But they must be vigorously and widely implemented to achieve the societal transformation required to decarbonise economies. A wide range of benefits will flow from a concerted effort to alter our energy economy now, including sustainable energy job growth, reductions in the health and economic costs of climate change, and the restoration of ecosystems and revitalisation of ecosystem services.

Key Message 6: Meeting the Challenge
To achieve the societal transformation required to meet the climate change challenge, we must overcome a number of significant constraints and seize critical opportunities. These include reducing inertia in social and economic systems; building on a growing public desire for governments to act on climate change; removing implicit and explicit subsidies; reducing the influence of vested interests that increase emissions and reduce resilience; enabling the shifts from ineffective governance and weak institutions to innovative leadership in government, the private sector and civil society; and engaging society in the transition to norms and practices that foster sustainability.
[UPDATE, 1:45 p.m.: A roundup of economists' and scientists' views at the Copenhagen climate meeting and a reaction from Mike Hulme, a participating scientist.]