What Is Black Carbon?
Black Carbon (BC) has recently emerged as a major contributor to global climate change, possibly second only to CO2 as the main driver of change. BC particles strongly absorb sunlight and give soot its black color. BC is produced both naturally and by human activities as a result of the incomplete combustion of fossil fuels, biofuels, and biomass. Primary sources include emissions from diesel engines, cook stoves, wood burning and forest fires. Reducing CO2 emissions is essential to avert the worst impacts of future climate change, but CO2 has such a long atmospheric lifetime that it will take several decades for CO2 concentrations to begin to stabilize after emissions reductions begin. In contrast, BC remains in the atmosphere for only a few weeks, so cutting its emissions would immediately reduce the rate of warming, particularly in the rapidly changing Arctic. Moreover, reduced exposure to BC provides public health co-benefits, especially in developing countries. Technologies that can reduce global BC emissions are available today.
Black Carbon and Climate Change
BC warms the climate in two ways. When suspended in air, BC absorbs sunlight and generates heat in the atmosphere, which warms the air and can affect regional cloud formation and precipitation patterns. When deposited on snow and ice, it absorbs sunlight, again generating heat, which warms both the air above and the snow and ice below, thus accelerating melting. Because BC remains in the atmosphere for only one to four weeks, its climate effects are strongly regional. Its short lifetime also means that its climate effects would dissipate quickly if black carbon emissions were reduced, thus benefiting most directly the countries or communities that invest in policies to reduce BC emissions.
A recent study suggests that BC may be responsible for more than 30 percent of recent warming in the Arctic, contributing to the acceleration of Arctic sea ice melting. Loss of Arctic sea ice would lead to more rapid warming and possibly irreversible climate change. BC is also driving increased melting of Himalayan glaciers, which are a major source of freshwater for millions of people in the region. BC may also be driving some of the observed reduction of the snowpack in the Pacific Northwest of the United States.
Different types of soot contain different amounts of BC—generally the blacker the soot, the more of a warming agent it is. Fossil fuel and biofuel soot are blacker than soot from biomass burning (e.g., forest fires and wood fuel), which is generally more of a brownish color. Thus, controlling emissions of soot from fuel sources is an effective way of reducing atmospheric temperatures in the short term. Based on current information, the United States is responsible for about 6 percent of global BC emissions; while it has a history of making reductions to improve air quality, further improvements can be made. The majority of BC emissions come from the developing world: China and India together account for some 25–35 percent of emissions.
Control technologies that reduce BC include retrofitting diesel vehicles with filters to capture BC, fuel switching (e.g., from diesel to natural gas in buses), and replacement of inefficient cook stoves with cleaner alternatives. Adopting these alternatives would have positive co-benefits for public health, especially in the developing world. For example, retrofitting or replacing diesel buses and trucks would greatly improve urban air quality in densely populated cities. Replacement of dirty cook stoves with cleaner alternatives, such as solar cookers or newer models that burn fuel more completely, would improve indoor air quality, which is a major health concern in both urban and rural areas of the developing world.
Reducing BC emissions represents a win-win scenario: it would have an immediate cooling effect on the Earth’s climate, potentially delaying temperature increases in the short run and helping reduce the risk of irreversible tipping points in the climate system, and it would reduce air pollution, resulting in fewer premature deaths and fewer missed work and school days.
2. BC is a carbonaceous aerosol. An aerosol is a suspension of fine solid particles or liquid droplets within a gas. Examples include smoke, air pollution, smog, oceanic haze, and tear gas. Carbonaceous refers to a substance rich in carbon.
5. The American Clean Energy and Security Act of 2009 reported out of the U.S. House Energy and Commerce Committee on May 21, 2009, has a significant section on BC emissions, directing the EPA Administrator to investigate BC sources, impacts, and mitigation technologies.
Most development and analysis of climate change policies have focused on reducing carbon dioxide and other greenhouse gases (GHGs), which are widely recognized as the major contributors to climate change. And as we blogged about last year, far less attention has been given to black carbon (BC). However things may be changing. Inspired by University of California – San Diego professor Veerabhadran Ramanathan’s Foreign Affairs article, “The Other Climate Changers,” the United States House Select Committee on Energy Independence and Global Warming held a hearing last Tuesday to investigate the impacts of black carbon pollution. The takeaway message from this hearing is that BC policies should be complementary to efforts to reduce GHG gases. Reductions in emissions of black carbon would have near-term effects on reducing global warming that are not possible from actions directed at carbon dioxide and other long-lived gases. Reducing BC is good for the environment, public health, and creates jobs. We recently published a detailed primer on BC science and policy.
Both professors Ramanathan and Tami Bond of University of Illinois at Urbana-Champaign gave an overview of the science of black carbon – uncombusted materials like soot and smoke. A growing body of evidence indicates that soot and smoke are major contributors, possibly second only to carbon dioxide, to human-induced global warming. BC warms the air by absorbing sunlight in the atmosphere, changes rainfall patterns and, when deposited on snow and ice, accelerates melting. According to Professor Ramanathan, BC’s warming effect is around 40 to 70 percent of that of carbon dioxide. However, unlike carbon dioxide, black carbon does not accumulate in the atmosphere; it stays in the atmosphere for a few weeks, so the impacts are more concentrated in the areas where they are produced, and reducing BC emissions would have near-term benefits in those areas.
BC is produced by both natural processes and human activity from the incomplete combustion of fossil fuels, biofuels, and biomass. According to Professor Ramanthan, the regional effects of BC are particularly large over the Arctic, Africa, and Asia. BC leads to increased melting of snow and ice in the Arctic, Sahelian drought, and decreased monsoon rainfall. Primary sources include diesel engines, small industrial sources, residential coal and solid biofuels for cooking and heating, and agricultural and forest fires.
Since the impacts of BC are regional, there are significant local environment, public health, and economic benefits of reducing BC emissions. Reducing BC emissions in India for example, would not only produce environmental benefits of cleaner air and negate rainfall loss, but would also save lives. Professor Ramanathan’s calculations indicate that replacing cook stoves in India with advanced biomass stoves could prevent 2 million deaths from the reduction of particulate matter produced by traditional stoves. Mitigating BC emissions would also prevent reduced rainfall and reduced agriculture yields.
According to another panelist, Conrad Schneider, Advocacy Director of the Clean Air Task Force, reducing BC emissions can create clean jobs here in the United States. Even though BC isn’t much of a climate forcing in the U.S. and a potentially expensive source of reductions, there is a billion dollars worth of work to reduce diesel’s BC emissions. For example, retrofitting 11 million diesel engines in the U.S. today could achieve the same environmental benefit as removing 21 million cars from the road, would save approximately 7,500 lives through reduced particulate matter pollution, and create tens of thousands of domestic jobs.
In order to get the environmental, economic, and public health benefits of reduced BC emissions, all the witnesses agreed that action must be taken. For more information, please check our white paper on the climate impacts of black carbon.
The following first appeared as a "Letter to the Editor" in today's Washington Post.
In his Feb. 21 op-ed column, "Global warming advocates ignore the boulders," George F. Will concluded, incorrectly, that the Earth isn't warming. Mr. Will referred to climate scientist Phil Jones, who said that the planet did warm from 1995 to 2009 but not "at the 95 percent significance level." But Mr. Jones also cautioned that 15 years is too short to expect statistical significance. That is why climate norms -- such as the "normal" daily temperatures that forecasters show on the local news -- are 30-year averages. The Post's readers might be interested to know, therefore, that the global warming trend from 1980 to 2009 -- a little over 1 degree Fahrenheit -- is statistically significant at the 99.9999 percent level.
Climate scientists have always stated clearly that it takes decades to detect a change in the climate, so why focus on just the last 15 years?
From its own reading of the peer-reviewed literature, the National Academy of Sciences concluded, "It is unequivocal that the climate is changing, and it is very likely that this is predominantly caused by the increasing human interference with the atmosphere. These changes will transform the environmental conditions on Earth unless counter-measures are taken."
This week, the National Journal Experts Blog asks: Can a U.N. probe calm the climate science storm?
In considering what should be done in light of recent revelations about aspects of the IPCC report, it is critical to distinguish between two different issues. One has to do with the IPCC itself. And yes, it is clear that here reforms are in order. The IPCC needs to clarify what sources can be cited in its reports, that all sources are properly verified, and that these guidelines are enforced. Because of the important role the IPCC report plays in international discussions, the standard for accuracy and reliability of everything it issues must be very high. The independent review announced by UNEP and a transparent discussion about these issues at the next IPCC plenary is a necessary and welcome step.
The second issue relates to our basic understanding of climate science. Here I think the answer is equally clear. None of what we have recently heard or read changes the basic scientific consensus that human activities have increased greenhouse gases in the atmosphere, that these greenhouse gases have raised temperatures (and the more we put into the atmosphere, the more temperatures will increase), that sea level has risen and ice cover declined as a result, and that unless we act now to slow future emissions, we should expect these changes to get worse over time.
The body of scientific evidence behind these concerns has developed and grown over decades of research. It is reflected in assessments by the National Academy of Sciences going as far back as the 1970s. And it is reflected in the IPCC’s physical science assessment, which remains above reproach three years after its release.
There seems to be some confusion out there about weather vs. climate. For example, a Virginia Republican Party video urged citizens to call their Congressmen and tell them how much global warming they got during the big snowstorm a couple of weeks ago. But that doesn’t really make any sense. In simple terms, weather determines whether you need to take an umbrella with you today; climate determines whether you need to own an umbrella. Weather determines whether you need your down coat today; climate determines whether you need to own a down coat. Weather determines whether you turn on your air conditioning unit today; climate determines whether you own an air conditioner. Weather determines whether the plants in your garden have a good day; climate determines what plants will likely thrive in your local environment.
Climate is the long-term average of weather. Weather changes all the time; climates are generally fairly stable, allowing us to make long-term decisions based on the notion that the future climate will be like the past. One unusual weather event does not mean the climate is changing. But many unusual weather events could mean the climate is changing. And climate change will mean that on average, the weather we will have in the future will be different from what we had in the past. That could even mean that record-breaking snowfall events happen more and more often in Virginia and Washington, D.C.
ANCHORAGE - "Hello. I'm a Republican, and I believe in climate change." These words opened a presentation at the Alaska Forum on the Environment and indicate that, here in Alaska, issues surrounding climate change have often transcended the partisanship that sometimes dominates the issue 3,000 miles away in Washington.
This bipartisanship has evolved because probably no place in America is the evidence of climate change more clearly on display than in Alaska. Climate change’s leading edge is in the Arctic, and temperatures in Alaska have risen 4 degrees or even more depending on location. With warming and its impacts visible to all and being increasingly analyzed on a local level, discussions of climate change, especially as it relates to adaptation, take on a tone all too unfamiliar inside the Beltway.
Here in Washington we’re waiting for the snow to end and Congress to make progress on a comprehensive climate and energy bill – both can’t come soon enough. And although the federal government has been closed here for the past few days, the past few weeks have seen some significant progress by federal agencies on the climate front.
As part of an effort to lead by example, President Obama announced that the federal government will reduce its greenhouse gas pollution by 28 percent by 2020. Federal agencies have been working on developing their targets since the release of President Obama’s Executive Order 13514 on Federal Sustainability in October of 2009, which requires agencies to set a number of measurable environmental performance goals. This target is the aggregate of 35 agency targets and the Obama Administration believes it will “reduce Federal energy use by the equivalent of 646 trillion BTUs, equal to 205 million barrels of oil, and taking 17 million cars off the road for one year.” Later this year federal agencies will be setting targets for their indirect GHG emissions (looking for GHG reduction opportunities with vendors and contractors, implementing low-carbon strategies for transit, travel, and conferencing, etc.).
We’ve also seen indications that the impacts of climate change are to be formally considered in the operations of two prominent federal agencies. The Pentagon released a long-term strategy that for the first time recognizes climate change as a direct threat to U.S. forces. In the Department of Defense (DOD) Quadrennial Defense Review (QDR) Report–the legislatively-mandated review of DOD strategy and priorities—the agency noted that climate change will affect DOD in two broad ways. First, it will shape the operating environment and missions by acting as “an accelerant of instability or conflict, placing a burden to respond on civilian institutions and militaries around the world.” And second, that DOD will need to adjust to the impacts of climate change on its facilities and military capabilities and will need to work to “assess, adapt to, and mitigate the impacts of climate change”.
The U.S. Securities and Exchange Commission (SEC) has announced that companies should disclose to investors the potential risks and opportunities that climate change presents for their assets. Although the guidance is not a formal regulation, the SEC intends for it to “provide clarity and enhance consistency for public companies and their investors”. In addition to the physical impacts of climate change (floods or hurricanes, rising sea levels, water availability, etc.), examples of where climate change may trigger disclosure requirements include the impacts of climate legislation and regulations, international accords, and indirect consequences of regulation or business trends.
These recent developments, along with the President’s clear commitment to climate change and energy policy during his State of the Union address last month are very encouraging.
Speaking of making progress, its time for me to get back to shoveling snow.
Heather Holsinger is a Senior Fellow for Domestic Policy
In the past few weeks I’ve posted twice (here and here) on reasons why global warming could be increasing the frequency of heavy snow events in certain parts of the United States (and likely in other similarly situated places around the world).
In a recent post on his WunderBlog (Weather Underground Blog), Dr. Jeff Masters gives his take on this issue. Dr. Masters is co-founder and Director of Meteorology of Weather Underground, a weather service that provides real-time weather information via the Internet. Unlike me, he’s a real weather expert and I highly recommend his blog.
- On the occasion of the Commerce Department's Proposal to Establish a NOAA Climate Service -
Statement of Eileen Claussen
President, Pew Center on Global Climate Change
February 8, 2010
It is clear that impacts from climate change are already being experienced across the United States and that our ability to manage and adapt to these changes will benefit from a comprehensive, coordinated Climate Service. The creation of a central clearinghouse in NOAA will help answer this critical and growing need for trusted information and resources.
Pew Center Contact: Tom Steinfeldt, 703-516-4146
Click here for NOAA press release
The cold weather continues across much of the Unites States, Europe, and central Asia as the Arctic Oscillation remains in a strong “negative” state, forcing cold Arctic air down to the mid-latitudes. A couple of weeks ago I explained why more frequent heavy snowfall events could be a consequence of global warming for mid-latitude areas near large bodies of water, like Washington, D.C., and Syracuse, New York (see figure).
|The average amount of annual snowfall has been increasing in Syracuse, New York, for most of the past century. (SOURCE: Increasing Great Lake–Effect Snowfall during the Twentieth Century: A Regional Response to Global Warming? Journal of Climate vol. 16, pp. 3535-3342, Figure 1)|
On January 31, I noticed a forecast for lake-effect snowfall around the Great Lakes on Weather.com: “Lake-effect snows are also possible near the central and western Great Lakes today and tonight.”