Two groups of scientists who this year published widely differing estimates of global carbon emissions from deforestation have now come to a consensus, thanks to an innovative collaboration designed to speed up the process by which scientific consensus is reached.
Presenting at Forest Day at a session facilitated by the Meridian Institute on the sidelines of the UN climate change talks in Doha, a group from the Woods Hole Research Center and one from Winrock International said they concurred that carbon emissions from tropical deforestation worldwide between 2000 andhttps://editorial.allafrica.com/working/editorial/in-progress/edit-batch.html?batch=1355281200-00010924-00-en&story_id=201212120189 2005 were 3 gigatons per year.
That's 3 billion tons of carbon dioxide, weighing more than 10 times the combined mass of all the humans on earth.
But the two groups didn't always agree. In fact, earlier this year, the Woods Hole group published a paper estimating global emissions from land use and land-use change from 2000 to 2010 to have been almost three times as much: 8.1 gigatons of carbon dioxide per year.
Each group is led by highly-regarded, credible scientists, says Daniel Zarin from the Climate and Land Use Alliance - so such seemingly different results led to confusion among policy-makers.
"The concern was that they came out with very different numbers, that seemed to indicate that there was a substantial disagreement about how large the amount of carbon emissions from tropical deforestation was," Zarin said.
"Science is going to inform policy making one way or another, it's either going to create confusion or it's going to create clarity. And in this space around the climate change negotiations, our experience is that when there's confusion about the science, it's an excuse for doing nothing."
So the Climate and Land Use Alliance, together with Norway's International Climate and Forest Initiative took an unusual step - and teamed up to convince the two groups to meet and try to find common ground.
"We wanted them to really talk about what their methodologies were, what the scope of their analyses were and to start to explore why they had such substantial differences in their results," Zarin said.
"The intent when we started wasn't actually to try to get to the same number, but rather for everyone to understand their differences in a way that was sufficiently clear to be able to communicate with both the scientific community and the policy-making community."
Animated discussions - and surprising results
The scientists met for two days in Washington DC.
"It was a very animated discussion at times," Nancy Harris from the Winrock team told the Forest Day audience.
"Those two days were a good opportunity for us to revisit what we had done in our own paper, and to dissect what the other group had done."
They discovered that the Woods Hole group - the one that reached the much higher estimate - included emissions from land use more broadly, including forest degradation - whereas the Winrock group focused strictly on deforestation. The Woods Hole group also included a longer time scale.
So the group from Woods Hole ran its analysis again to align its scope more closely with the simpler Winrock study, so the two could be directly compared. They did this by excluding activities leading to forest degradation, and focussing on the period 2000-2005.
Remarkably, even though the methods, underlying data sets and models used were different, they did in fact reach the same number: 3 billion tons of carbon dioxide emissions from tropical deforestation per year from 2000-2005, excluding emissions from mineral soils and peat.
This means that researchers have now given policy-makers an unbiased, historic benchmark to use in discussing agreement on a target of reducing emissions from tropical deforestation, says Zarin.
"That should help policy makers because one of the things that is really important in this process is to know what your benchmark is that you're measuring things against," he said.
"Over the past few years a number of groups including the European Union have set rather vague targets, including cutting deforestation emissions in half. Now that remains a kind of theoretical target until you know in half of what."
"So now we have a benchmark that has been approved by two different kinds of approaches and can serve as a means against which to both make those targets and measure progress."
Accelerating the process
The unusual step of getting opposing groups of scientists together in a room to thrash out their differences is a method Zarin would like to see adopted more often - especially in fields like climate change where time is of the essence, and we can't wait 30 years for gradual consensus building.
"There's an underlying purpose here to reduce emissions at the global level in order to avoid catastrophic climate change globally," he said.
"Because we're in a space that is so important for policy making, particularly now that we're clearly failing globally to deliver on climate change mitigation that's needed, we really need to understand where we are with deforestation."
"Deforestation is one place where there is progress being made, and it is possible to actually reduce these emissions very substantially in the near term," he said.
"So for that reason accelerating this process by which science progresses and gets to better and more accurate results over time, is a priority."
"I think there's a lot of opportunity to work at encouraging scientists to very quickly resolve their differences. Not necessarily striving to get the same result, but striving to understand why results are different at a level that is meaningful, that can be worked on, and that's transparent for the rest of the scientific community and for policy makers to understand."