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Explainer: How Much Carbon Can The World’s Forests Absorb?
11 June 2013, 5.35am BST Explainer: how much carbon can the world’s forests absorb? AUTHOR Peter Reich Scientific advisor, Hawkesbury Institute of the Environment at University of Western Sydney DISCLOSURE STATEMENT Peter Reich does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations. Provides funding as a Member of The Conversation. uws.edu.au If deforestation is cut down, the world’s forests could act as a large net sink for carbon emissions. Flickr/sobriquet.net You are walking through the bush when you see an enormous tree trunk, tens of metres long, lying across the forest floor. Imagine you and several dozen friends lifting it by hand. Now you’ve literally grasped the significance of trees and forests when it comes to carbon sequestration – trees are heavy, and carbon accounts for almost half their dry weight, or biomass. The world’s forests are a net carbon “sink”. Each year they remove more carbon from the atmosphere by photosynthesis than they return via their own respiration, decomposition of dead roots, trunks and leaves, and by forest fires. That is how the growth and re-growth of forests around the world has slowed climate change in the past century. It has been estimated that between one-third and one-fourth of the total carbon dioxide (CO 2 ) emissions from burning coal, gas and petrol has been turned into wood and other plant parts through this process. Without that incredible ecosystem service, climate change would be much more extreme today than it already is. Despite advances in satellite remote sensing and ground inventories, our estimate of the area covered by forests globally is surprisingly shaky. We are unsure how much the trunks of all those trees weigh, nor can we know for certain the weight of their roots. It is even harder to figure out how much the total global forest biomass grows from one year to the next – a key figure that tells us how much of our annual CO 2 pollution has been scrubbed out of the air by forests. Forest ecologists like a challenge however, and there have been several attempts at estimating the forest carbon “sink”. Perhaps the most internationally comprehensive approach was an assessment of forest carbon stocks and fluxes across the globe between 1990 and 2007. They assessed the carbon content of live biomass, dead wood, litter, oil organic matter and harvested wood products in tropical, temperate and boreal forests, and examined how these stocks changed over roughly two decades. According to this analysis, intact forests and those re-growing after disturbance (like harvesting or windthrow ) sequestered around 4 billion tonnes of carbon per year over the measurement period — equivalent to almost 60% of emissions from fossil fuel burning and cement production combined. This news is not as good as it seems. During the time measured, tropical deforestation resulted in the release of almost 3 billion tonnes per year. Thus, globally, the net forest carbon sink amounted to just 1.1 billion tonnes per year or one-seventh of average emissions from fossil fuel burning and cement production over the period measured. These numbers suggest that forests, and tropical forests in particular, could play a key role in slowing the rise of atmospheric CO 2 in the decades to come. In the tropics, growth and re-growth of forests generated a colossal carbon sink of 2.8 billion tonnes of carbon per year. This largely, but not entirely, counterbalanced the equally colossal carbon emissions associated with deforestation of other tropical forests. As a result, the tropics served as a relatively small net source of carbon to the atmosphere since 1990. If deforestation continues unabated, and droughts and forest fires become more common, as is expected, then tropical forests could become a large net source of carbon to the atmosphere, heating up the pace of climate change. Disturbances to temperate and boreal forests from climate change-induced droughts, wildfires and windstorms could make the situation even worse. Conversely, if deforestation was to slow in comparison to continued growth of recovering and intact forests, tropical forests could serve as a large net sink of carbon in the future and make the United Nation’s Reducing Emissions from Deforestation and Forest Degradation ( REDD ) programme a meaningful contributor to offsetting emissions. Our best estimates of global forest carbon sinks and sources demonstrate the ongoing importance of forests to the global carbon cycle. Unfortunately, however, they do not provide a road map to the future. If forest “scrubbing of CO 2 ” declines while release of CO 2 remains stable or grows, the “braking” effect of the world’s forests on the pace of climate change will grow weaker, perhaps disappearing entirely. That would be truly bad news for the global climate and those who depend on it. And unfortunately, that is not just a lot of hot air. Continue reading
Airlines Push for Global Measures to Control Carbon Emissions
By CHRISTOPHER F. SCHUETZE Fabrice Coffrini/Agence France-Presse — Getty Images Geneva International Airport. Airline travel is thought to cause 2 percent to 3 percent of the world’s carbon emissions. Last week, airlines called on the aviation authorities to find a way to curb emissions after 2020.Despite the unpopularity of a European aviation carbon emission tax, the world’s airlines are ready to discuss global measures. The announcement , which calls on the International Civil Aviation Organization, the civilian sky’s U.N. regulating body, to adopt an across-the-board, market-based mechanism to offset emissions, was made during the International Air Transport Association’s 69 th annual meeting, in Cape Town. “We can give them a direction we want them to go,” said Tony Tyler, the head of the association, about the recommendations to the governing body in a video statement . The International Civil Aviation Organization hopes to steer governments away from a patchwork of national rules and toward a single, global, market-based mechanism. “Such a patchwork would be an administrative nightmare,” said Paul Steele, the association’s environmental director at a news conference . The industry group represents 240 of the world’s airlines, which operate 84 percent of all civilian flights. The association has called for environmental standards before, but this is the first time it has called for comprehensive binding regulations. Since 2010, the association has been in favor of a 1.5 percent annual increase in fuel efficiency from 2010 to 2020, with carbon neutral growth by 2020. By 2050, the association wants net emissions cut by 50 percent from 2005 levels. As Rendezvous reported last year , Europe and the rest of the world have been in disagreement over whether foreign carriers should take part in the European Emission Trading System when landing at European destinations. A European Union rule, in place since last year, would have taxed carbon emissions on flights terminating or originating in Europe, even for non-European airlines. Last summer, a group of non-European nations met in Washington to condemn such taxation. Then President Barack Obama disappointed environmentalists when he signed a bill into law that actually prohibits United States airlines from paying the tax when landing in Europe, in contravention of international law. Earlier this year, the European Union announced a “stopping of the clock” in its demand for non-European carriers to participate in its emission trading program. At the time, Connie Hedegaard, the E.U. commissioner for climate action, described the move as allowing the rest of world to catch up. The air association’s most recent announcement was welcomed in Brussels. “It is a very strong message that the airline industry seems ready to support a single global market-based measure to keep their emissions in check,” Ms. Hedegaard said in a statement sent to reporters last week. “The E.U. is ready,” she said. Airline travel is thought to cause 2 percent to 3 percent of the world’s carbon emissions. According to a National Geographic report , an average passenger airplane burns four liters, or a little more than a gallon, of jet fuel for each kilometer each a passenger flies. This number is already a 40 percent improvement over jet fuel efficiency in 2000. Though the number of flights may still be climbing (Rendezvous reported last year on the one billionth international arrival in 2012), new planes are becoming increasingly fuel-efficient. “This is a responsible industry. We are the only industry in the world that has set itself clear targets in terms of emission standards,” said Mr. Tyler, according to the video statement. Continue reading
Silver Linings In The IEA Report On 2012 Fossil Fuel Carbon Emissions
Carbon emissions from fossil fuels reached record levels, but the 2012 rise was relatively small, and there are positive signs China’s energy mix is becoming less carbon intensive. Photograph: Bei Feng/EPA As Fiona Harvey reported for The Guardian, the International Energy Agency (IEA) 2012 World Energy Outlook Report found that annual carbon dioxide emissions from fossil fuels rose 1.4 percent in 2012 to 31.6 billion tonnes (gigatonnes [Gt]). The bad news is that this is a new record high level of emissions. The good news is that it represents the second-smallest annual increase since 2003, behind only 2009 when global fossil fuel carbon emissions fell due to the global recession. Emissions estimates from 2009–2010 have also been revised downward, so the reported 31.6 Gt 2012 emissions match the reported value from 2011 . American emissions of carbon dioxide from fossil fuels fell by 200 million tonnes (Mt) to levels last seen in the mid-1990s due to a transition from coal power to natural gas and renewable energy . European emissions fell 50 Mt due to economic contraction and renewable energy growth, despite an increase in coal energy use. Perhaps most encouraging, although Chinese emissions grew by 300 Mt in 2012, this was among the country’s smallest annual emissions growth over the past decade. This is a result of China diversifying its energy sources and installing more renewable energy. Chinese CO2 emissions per unit of electricity generation since 2000 The IEA report comes on the heels of an agreement between the presidents of USA and China to reduce emissions of hydrofluorocarbons (HFCs), which are potent greenhouse gases. This could potentially lead to the reduction the equivalent of 90 Gt of carbon dioxide by 2050, or nearly three years of current global emissions from fossil fuel use. China is also considering putting a price on its carbon emissions, and their goal is to end the rapid growth of Chinese coal power use . So there are signs that the world’s two largest greenhouse gas emitters, USA and China are beginning to take serious steps to address the climate problem. The question is whether those steps will be large enough and fast enough to avoid triggering dangerous climate change . At the moment, we our emissions are closest to Scenario A2 from the 2007 Intergovernmental Panel on Climate Change (IPCC) report. IEA emissions vs. IPCC scenarios Scenario A2 represents 3 to 4°C global surface warming by 2100 as compared to pre-industrial levels. This far exceeds the internationally accepted 2°C “danger limit” , and would put us at serious risk of catastrophic climate change . However, the relatively small emissions increase in 2012 has pushed us in the direction of IPCC scenario A1T, which represents 2 to 3°C warming by 2100. That still exceeds the danger limit, but at least it’s movement in the right direction. More still needs to be done to reduce our fossil fuel consumption. To have a realistic chance of avoiding 2°C warming, emissions need to peak by the year 2020. The earlier they peak, the better chance we have of limiting the impacts of climate change to an adaptable level. This will be challenging, because power plants have lifetimes of many decades, so we’re already “locked in” to a substantial chunk of emissions from those that have already been constructed or are in construction. The IEA report presented four recommendations for limiting global warming to 2°C: 1) Increase energy efficiency in buildings, transportation, and industry. 2) Limit the construction and use of inefficient coal power plants. 3) Minimize methane emissions from oil and gas production. 4) Accelerate the phase-out of fossil fuel subsidies . The positive movement from China and the USA in particular is encouraging, but we still have a lot of work ahead to turn the annual carbon emissions growth into an annual decline in order to limit the climate damage to adaptable levels. Continue reading
