The text version includes the phrase "Local smoke", which usually has other connotations out here on the West Coast.
It is very hazy outside, but the situation is far worse across the world in Moscow.
Showing posts with label forests. Show all posts
Showing posts with label forests. Show all posts
Thursday, August 05, 2010
Yes, this is the Environment Canada forecast for Vancouver
The text version includes the phrase "Local smoke", which usually has other connotations out here on the West Coast.
It is very hazy outside, but the situation is far worse across the world in Moscow.
Sunday, April 27, 2008
The pine beetle and carbon cycle feedbacks
An important study from in last week’s Nature concluded that the mountain pine beetle infestation that have devastated the forest industry out here has also converted western Canadian forest from a carbon sink to a carbon source. In the simplest possible terms, the beetles kill the trees, decreasing carbon uptake (photosynthesis) and increase carbon loss (decomposition). This is not a new suggestion. The Kurtz et al. paper is, however, the most complete accounting to date.
A lot of people are labelling this a ‘positive feedback’ from climate change (e.g. like how warming melts sea ice, which reduces reflection of solar radiation, which accelerates the warming). The logic is that warmer weather promotes the beetle outbreak, which releases carbon from the forest, which further warms the climate.
The assertion appears correct. But be wary of the hyperbole. Not all positive feedbacks are made equal. There are only so many pines, the beetles can only do so much damage. At some point, they run out of trees to eat, and the infestation recedes. As the authors of the Nature study have said, the betters have almost eaten themselves out of house and home. And re-forestation initiatives could return the forests to being a carbon sink.
The type of positive feedback that should be included in carbon cycle assessments? Yes. Runaway positive feedback that will send the atmosphere to 1500 ppm? Probably not.
There is a sadly ironic policy twist to the beetle infestation. For one, the forests now might pump out more carbon than the entire BC economy, throwing a wrench into regional GHG reduction agreements. The Canadian government lobbied hard to include forest carbon sinks under the Kyoto process, under the expectation that our boreal forest would provide a big carbon credit and reduce the need to address emissions themselves. Safe to say, that stance has softened in recent years.
Tuesday, February 12, 2008
Biofuels and the "land use cascade"
As readers of Maribo no doubt heard, two papers in last week’s Science addressed the greenhouse gas emissions that arise from clearing lands for biofuel crop production. It is an important subject that has been widely discussed within the scientific community, including my own collection of colleagues, for the past year or two. You might say these papers are the first to “do the math”. The papers conclude what many carbon cycle experts suspect: that any greenhouse gas benefits that come from using biofuels instead of oil are negated when you include the emissions associated with land clearing.
The publication of both papers at once is enlightening because they tackle slightly different, but complimentary, issues.
Fargione et al. address the direct emissions from the land cleared to plant the actual biofuel crops. The examples includes Brazilian Amazon to soybean biodiesel, Brazilian Cerrado to soybean biodiesel, Brazilian Cerrado to sugarcane ethanol, Indonesian or Malaysian lowland tropical rainforest to palm biodiesel, Indonesian or Malaysian peatland tropical rainforest to palm biodiesel, and US Central grassland to corn ethanol.
Searchinger et al. use a global economic model to look more at the indirect emissions. In the developed world, including Canada and the US , forests or grasslands are not being cleared to plant biofuel crops. Instead, biofuels are being produced on land previously devoted to other crops or from grain diverted from another use (i.e. corn grain goes to the ethanol plant rather than the boat shipping it overseas). The change has a cascading effect on the world market. There is less grain available, which can cause other countries to clear land to feed the market.
I like to call problems like that addressed in the Searchinger et al. paper “land use cascades”. There are countless examples -- one of the my favourites is the effect that the surge in soybean production in the US and Brazil in the 90s had on the Yasawa Islands in Fiji (I tell the whole story is here).
These cascades are becoming increasingly important, and increasingly global in scale. For example, the same thinking needs to be applied to forestry-based carbon credit programs. If a segment of BC coastal rainforest slated for logging is protected, does that mean some other forest must be logged to provide the missing pulp and paper? If so, what effect does that have on the net emissions? We may discover that net greenhouse gas savings only occur if we also reduce demand for the products that would otherwise come from that land either cleared (biofuels) or saved (forest carbon credits). More on that later.
Thursday, August 16, 2007
Reporting and promoting science
Science sells these days. In the push for advertising dollars and readership, the conventional and electronic media strive to link new scientific results to the pressing issues of the day.
And, to be fair, in the push for tenure and grant dollars, we academics can be guilty of the same. The holy grail used to be getting a paper in Nature or Science. Now it is getting a paper in Nature or Science so that the paper will be reported on CNN or the BBC.
The intent, in either case, can be benign. A lot of the published science today, on subjects like climate change, is important news. But in the effort to "frame" - to use the terminology in the Matt Nisbet and Chris Mooney article that created buzz earlier this year - science for public and political consumption, a lot of mistakes are being made. It ranges from the inaccurate reporting and questionable publicity of the mythical lake that would resolve the very real crisis in Darfur to outright abuse of statistics to throw stones at solid science.
Take these three recent headlines... please.
1
I call this is a "false positive". There's been a huge and unnecessary uproar over the discovery of a minor mathematical error in the NASA GISS historical temperature dataset. The error means that 1998 was no in fact the warmest year in US history, but is tied with 1934. As the NASA scientists themselves report (pdf), the error has a negligible impact on the global temperature, no impact on global rankings of the warmest years, and absolutely no impact on the evidence for human influence on the climate (see Tamino or Realclimate for details).
2) Warming will pause then full steam ahead, scientists contend
This is the "we didn't read the whole paper". These reports of a "global warming" forecast for the next decade come from a innovative short-term climate modeling study published in Science. The goal of the study was to test the ability to predict climate on decadal or shorter time-scales, a specially developed climate model that explicitly considers the frequency of large-scale atmosphere-ocean oscillations like El Nino (see Tamino). At the end of the study, after a lengthy model validation against observed data from the recent past, the authors discuss the model's predictions for the next ten years, stressing they are contingent on stochastic variables like the occurrence of El Ninos. The headlines made it seem as though the scientific community had confidently concluded that 'warming will pause' for a couple years.
3) Trees won't fix global warming
And finally, "we just didn't understand the paper". The headlines are based on research, presented at last week's ESA meeting, from Duke University's Free Air Carbon Enrichment (FACE) site, where scientists have been testing the effect of higher CO2 levels on tree growth for the past ten years. In the past, scientists had thought that higher atmospheric CO2 would effectively 'fertilize' plants. The Duke experiments showed that this fertilization effect was limited by the availability of water and nutrients (press release). In an effort to link the result to a public issue - carbon offsets - the media stories reported that new research shows planting trees won't work to combat global warming. In other words, planting trees won't take up ANY carbon. Of course it would; all that wood is made of carbon, where else could it come from? The Duke research only showed that there won’t be an extra growth bump because there’s more CO2 levels in the air, not that there won't be any growth at all.
This is the danger of popularizing science. As we saw with the coverage of the Darfur Lake, more attention was given to the initial headline than to the later reports that the 'lake' did not in fact hold any water. Unfortunately, with such quick turnaround in reporting, it is vital that all of us, the one's doing the research, the one's writing the press releases and the one's writing the news story, get it right the first time. It's not a trivial task. But otherwise, these misrepresentations (about global temperature) or misintepretations (about short-term climate prediction) or mistakes (about trees and carbon) make it into the public consciousness.
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