Climate 411

NOAA Report Confirms: Yes, the World Is Warming

A report released this week by the National Oceanic and Atmospheric Administration (NOAA) provides new evidence that global warming continues relentlessly.  The report comes after climate science was found to be solid in several official investigations into the so-called “Climategate” controversy, and it adds even more urgency to the need to reduce global warming pollution to prevent severe impacts in the future.

The report, “State of the Climate in 2009,” was authored by more than 300 scientists from 160 research groups in 48 countries.  It confirms that each of the past three decades was warmer than the last, with the 2000s being the warmest in the 150-year record.

The latest data from all the regions of the world are presented for a variety of climate indicators.  Ten of the indicators most closely related to surface temperature all support the idea that the Earth is warming.

Specifically, seven indicators are rising, indicating a warming world:

  • air temperature over land
  • sea-surface temperature
  • air temperature over oceans
  • sea level
  • total heat content of the ocean
  • humidity
  • tropospheric temperature (in the “active-weather” layer of the atmosphere closest to the Earth’s surface)

And three indicators are declining, also indicating a warming world:

  • Arctic sea ice
  • glaciers around the world
  • spring snow cover in the Northern hemisphere

These climate indicators represent many independent lines of evidence for global warming.

This report comes on top of a set of recent reports by the National Academy of Sciences that provide yet more evidence that human-produced pollution has caused the warming observed over the past several decades and that continued warming poses serious and costly risks to society.  Together, these latest scientific reports show that global warming is happening and will only get worse unless we seriously cut back our global warming pollution.

As evidenced yet again by the new NOAA report, the science is very clear:  We must begin cutting our emissions now to avoid even more dramatic cuts later, since global warming gases stay in the atmosphere for decades or even centuries and keep accumulating there. A delay of two or three years will make the necessary pollution cuts more severe and expensive.

My colleague Chris Scott will in touch regarding sending the proposal to you. If you need to contact us at all next week, please call or email Chris on +44 1722 320596 or
Posted in News, Science / Comments are closed

Clearing Up Confusion: The Recent Cold Snap and Global Warming

Our bitter cold winter has become one of the hottest topics of conversation in America.

Specifically, people are talking about how a severe cold snap can occur at the same time as global warming. If you haven’t seen it yet, check out the debate on the Washington Post website.  In this post, I’ll try to clear up two of the issues that emerged from that debate:

  1. What does a particular cold spell say about global warming, and
  2. If the recent cold spell doesn’t disprove global warming, does that also mean that other kinds of extreme weather, like heat waves, aren’t caused by global warming?

Climate versus weather

All of the Post’s panelists were careful enough to explain the difference between weather and climate: Climate refers to the average weather over a long period. For the most part, they did not fall for the common mistake of interpreting a cold spell as evidence against global warming.

Here’s what’s been happening with the weather recently: There have indeed been below-average temperatures recently in much of the eastern U.S. and in parts of Europe, Russia, northern China, and northern India. But at the same time, there were above-average temperatures in the western U.S., eastern Canada and Greenland, some other parts of the Arctic, North Africa and Central Asia, as this map shows.

NOAA map of worldwide temperatures

This distinct pattern of temperatures was caused by an unusually persistent version of an atmospheric flow pattern known as a “Greenland block.”  This Greenland block diverted frigid Arctic air far to the south in eastern North America and Europe. (More about it on the Weather Channel: “Why So Cold? Blame the Greenland Block.”)

It’s important to look at weather events like cold snaps in context—we can have a relatively brief spell of cold weather in certain regions even while the global climate is warming.  All the evidence shows that the world overall has been warming over the past several decades. (See a chart in a post on this same topic by Lisa Moore in 2008.)

So how do we know if the climate is warming? We look at a wide range of long-term trends. Along with rising air and ocean temperatures, the other signs of a warming climate include rising sea level, retreat of glaciers in most regions, rapid shrinkage of summer sea ice in the Arctic, and shifts in species distributions and seasonal behavior.

Global warming does cause more extreme weather

Although the Post’s panelists were accurate on the first issue, there could have been more discussion on the fact that global warming does have an effect on some kinds of extreme weather. One of the panelists even claimed that extreme events like heat waves cannot be used as evidence of global warming. That is wrong, so let’s look at how the frequency and intensity of certain extreme weather events are expected to increase under global warming.

Records indicate that there has already been an increase in intensity and frequency of heat waves and heavy rainfall in many parts of the world over the past several decades.  (See “Frequently Asked Question” number 3.3 excerpted from the 2007 IPCC report [PDF].)  Why? Global warming drives a rise in average temperature and atmospheric moisture, promoting more heat waves and torrential downpours. On top of that, changes in atmospheric circulation patterns caused by global warming are also thought to contribute to stronger heat waves.

There will still be variations from year to year, but on average, these extreme events will increase over time as the Earth warms.  On the other hand, extremely cold temperatures are becoming less common — but can still occur — as heat builds up in the climate system.

Of course, individual weather events should not be blamed on global warming, just as an individual cold snap doesn’t disprove global warming. EDF has been careful not to attribute individual events to global warming.  Instead, we point to examples of what we expect to see more and more of in the future if we don’t fight global warming.

And with the trends in extreme weather we’re already seeing, that future ain’t lookin’ pretty.

Posted in Extreme Weather, Science / Read 15 Responses

Opportunity: Reduce emissions of the overlooked accomplices of CO2

The global warming culprit we hear the most about is carbon dioxide (CO2), but human activity produces a host of other, shorter-lived pollutants that act as “partners in crime” in contributing to climate change.

Until recently, most of the attention paid to these pollutants has centered around their detrimental effects on air quality and human health – the pollutants include fine particles such as black carbon and gases that form smog.

But because these pollutants disappear from the atmosphere relatively quickly, they also give us an important opportunity to put the brakes on the rapid rise in global temperature. If people around the world can reduce the amounts that they emit, everyone will see an immediate benefit and help avoid dangerous tipping points in the climate system over the next few decades.

My colleagues Nadine Unger and Drew Shindell at the NASA Goddard Institute for Space Studies (GISS) and I just published a paper in the journal Atmospheric Environment that offers additional insight into the climatic role of these pollutants. Our findings come at a time when activity on domestic and international climate policy in general and on black carbon policy in particular is ramping up.

For this paper, we delved into emissions from two key sectors, transportation and power generation, for the U.S. and the world. We primarily used a global climate model developed at NASA GISS that simulates the transport of pollutants by wind and the chemical and physical reactions that transform the pollutants into smog and particles. The model also calculates the warming or cooling effect of the different pollutants.

One of our important findings is that transportation is a particularly good sector to target quickly for emissions controls because it produces a lot of black carbon (think: diesel exhaust) and ozone-producing gases, in addition to CO2. In contrast, emissions cuts in the power generation sector do not offer the same short-term opportunity. That sector emits little black carbon, but it does create much sulfate particle pollution. Sulfate particles are bad for air quality and acid rain, but in the short term actually counteract the warming effects of CO2 emissions. Of course, it is essential to clean up the power sector to address long-term climate damage from CO2, as well as health problems from sulfate particles, ozone smog and other pollutants. But short-term opportunities to slow global warming are more significant in the transportation sector.

We also considered a hypothetical example of switching the transportation sector to a zero-emissions or electric power source, such as in plug-in hybrid electric or pure electric technologies.The result: A hefty benefit for the climate.

The switch to a zero-emissions or electric power source would decrease the warming effect if you just consider CO2 emissions.  (Though increased CO2 emissions from the electricity generation sector would offset the decrease in direct emissions from vehicles to a certain extent.)

But reducing the non-CO2 pollutants provides even more benefit for the climate. Zero-emission or electric transportation would greatly reduce black carbon emissions.  The short-term benefits to be gained from focus on the transportation sector are important for policymakers to note.

Last week’s announcement by President Obama on national greenhouse gas emissions standards for passenger cars and light trucks is a significant step in this direction. Further action is needed to clean up the exhaust from existing heavy-duty trucks and other diesel-powered transport, both in this country and internationally.

Unger and her colleagues are working to expand the published analysis to include a full suite of economic sectors, including industry, non-road transport and agriculture, and additional greenhouse gases such as methane and nitrous oxide.

Look for another paper in the near future.

Posted in Cars and Pollution, Science / Read 2 Responses

An Engaging, Eye-Pleasing Summary of Global Warming Science

James Wang's profileDire PredictionsWe frequently mention the IPCC reports on Climate 411 – often referencing them as the most trustworthy authority on global warming science. In fact, our very first blog post was titled "What is the IPCC, anyway?" But for non-scientists, these rather technical reports are a challenge to read.

Climate scientists Michael Mann and Lee Kump published the book Dire Predictions to make the IPCC’s crucially important findings accessible to the layperson. For the most part, they succeed admirably. Mann and Kump did a remarkable job of simplifying complex ideas. But it still gets a little dense in places.

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Carbon Dioxide Emissions Up 3 Percent in 2007

James Wang's profile2007 EmissionsLast Thursday, the Global Carbon Project released its annual report on the state of the carbon cycle, Carbon Budget 2007 [PDF]. It emphasizes (as we reported earlier this year) that CO2 levels are continuing upward, and the rate of increase is accelerating.

One reason for the acceleration in CO2 concentrations is higher fossil fuel emissions. Despite rising fuel prices, global CO2 emissions from fossil fuels rose 3 percent in 2007. That’s just slightly below the average increase of 3.5 percent per year since 2000.

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Did Humans Cause the Midwest Flooding?

James WangThis post is by James Wang, Ph.D., a climate scientist at Environmental Defense.

The record floodwaters in Iowa and other parts of the Midwest are claiming lives, destroying homes and crops, contaminating drinking water, and – as the AP puts it – spreading "a noxious brew of sewage, farm chemicals, and fuel that could sicken anyone who wades in." The cost in human anguish is incalculable.

But why is it happening? Is it just a freak of nature? One causal element, as reported in today’s Washington Post, may be human reengineering of the landscape. Mary Kelly, who heads up EDF’s rivers and deltas program, gives a good overview of these issues.

Another element may be global warming, which increases the probability of extreme weather events like torrential rain.

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Posted in News / Read 12 Responses