350 Science

If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO2 will need to be reduced from its current 385 ppm to at most 350 ppm.

There are three numbers you need to really understand global warming, none of them very complicated. For all of human history until about 200 years ago, our atmosphere contained 275 parts per million of carbon dioxide (that's the first number). Parts per million simply means the ratio of the number of carbon dioxide molecules per million other molecules in the atmosphere. That much CO2 is useful-without it the earth would be very cold, like Mars. So we need some carbon in the atmosphere; the question is how much?
 
Beginning in the 18th century, we started to burn coal and gas and oil to produce energy and goods.  The amount of carbon in the atmosphere began to rise, at first slowly and now more quickly. Many of the activities we do every day like turning the lights on, cooking food, or heating or cooling our homes rely on energy sources like coal and oil that emit carbon dioxide and other heat-trapping gases into the atmosphere. We're taking millions of years worth of carbon, stored beneath the earth as fossil fuels, and releasing it into the atmosphere. By now-and this is the second number-the planet has 387 parts per million CO2 - and this number is rising by about 2 parts per million every year.
 
Scientists are now saying that's too much - that number is higher than any time seen in the recorded history of our planet - and we're already beginning to see disastrous impacts on people and places all over the world. Glaciers everywhere are melting fast-and they are a source of drinking water for hundreds of millions of people. Mosquitoes, who like a warmer world, are spreading into lots of new places, and bringing malaria and dengue fever with them. Drought is becoming much more common, making food harder to grow in many places. Sea levels have begun to rise, and scientists warn that they could go up as much as several meters this century. If that happens, many of the world's cities, island nations, and farmland will be underwater. These impacts are combining to exacerbate conflicts and security issues in already resource-strapped regions.
 
In the past year, some of the world's leading climate scientists have told us what the highest safe level of CO2 is: 350 parts per million. That's the last number you need to know, and the most important. It's the safety zone for planet earth. As James Hansen of America's National Aeronautics and Space Administration, the first scientist to warn about global warming more than two decades ago, wrote recently, "If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO2 will need to be reduced from its current 385 ppm to at most 350 ppm."
 
That will be a hard task, but not impossible. We need to stop taking that carbon out of the ground and putting it into the air. Above all, that means we need to stop burning so much coal-and start using solar and wind energy and other such sources of renewable energy -while ensuring the Global South a fair chance to develop. If we do, then the earth will slowly cycle some of that extra carbon out of the atmosphere, and eventually we'll return to a safe level. By decreasing use of other fossil fuels, and improving agricultural and forestry practices around the world, we could get back to 350 by mid-century. But the longer we remain in the danger zone-above 350-the more likely that we will see disastrous climate impacts.
 
Every year since 1992, the United Nations hosts a two-week long conference for world leaders to meet and discuss what to do to about the global threat of climate change. In December of 2009, this meeting will be in Copenhagen, Denmark. There, delegates, non-governmental organizations, and businesses from every nation will meet to forge a new global climate change agreement. Right now, the numbers in the discussion are 450ppm and 550ppm, which scientists are now saying are far outside of the safe zone, and ensure disaster for our planet's future. It's no small task, but we need to let our world leaders know that 350 is the safe target that can ensure an equitable future and save us from climate catastrophe.
 
With your help, we can spread the word to our fellow citizens, communities, countries, and the world that we need to aim for 350 and why.
 
Join the movement.
 
Sources - Lots of people know plenty more than we do about
global warming, its impacts, and solutions- below is a short list of
resources for basic information on global warming, as well as current
information about the latest studies and articles related to climate
science, impacts, and policies. If you think we're missing something
really important, let us know.
 
Climate Science and Policy Resources - mainly English scientific
articles and helpful blogs to help fully understand global warming
science, policy, and impacts
 
Hansen, James, et al. Target Atmospheric CO2: Where Should Humanity
Aim? Submitted April 7, 2008. NASA climate scientist James
Hansen's paper about the 350ppm target.
 
Hansen, James, et al. Target Atmospheric CO2: Supporting Material. Submitted April 7, 2008.
 
The IPCC 4th Assessment Report - link to the latest report by the
Nobel-prize winning United Nations Intergovernmental Panel on Climate
Change, supported by the world's leading climatologists.
 
Baer, Paul, Tom Athanasiou and Sivan Kartha. "The Right to Develop
in a Climate Constrained World: The Greenhouse Development Rights
Framework" - an important policy framework for how to mitigate climate
change while ensuring an equitable path to development for the Global
South.
 
The United Nations Framework Convention on Climate Change - link to
the official UNFCCC website with information about the UN climate
policy process.
 
RealClimate - A climate change blog, run by climate scientists.
 
Recent News Articles - recent articles about the increasing urgency of climate science, and severity of climate impacts

Ban Ki Moon. "A Climate Culprit in Darfur." The Washington Post. June 16, 2007.

German Advisory Council on Global Change. "World in Transition - Climate Change as a Security Risk". January 2008.

Ghosh, Pallab. "Climate Set for Sudden Shifts." February 4, 2008. BBC News.

Moore-Lappé, Frances. "Ice Melt Accelerates Around the World". February 4, 2008. Earth Policy Institute.

McInnis, Laura. "Climate Change Threatens Human Rights of Millions: UN." February 19, 2008. Reuters.

MacKenzie, Debora. "Melting Glaciers will trigger food shortages". March 20, 2008. NewScientist.com news service.

Pilkington, Ed. "Climate Target is not Radical Enough - Study". April 7, 2008. The Guardian.

Lovell, Jeremy. "Poor Children Main Victims of Climate Change: UN." April 28, 2008. Reuters.

Morris, Nigels. "Climate change could force 1 billion from their homes by 2050" April 30, 2008. The Independent.