A new world?: carbon dioxide concentrations in atmosphere hit 400 ppm

Jeremy Hance
mongabay.com
May 11, 2013



For the first time since homo sapiens evolved, concentrations of carbon dioxide in the atmosphere have struck 400 parts per million (ppm) due to burning fossil fuels. The National Oceanic and Atmospheric Administration (NOAA) reports that readings of carbon dioxide at Mauna Loa Observatory in Hawaii hit the symbolic number on Thursday and are expected to continue rising in coming years. The last time concentrations were this high for a sustained period was 4-5 million years ago when sea levels were 5-40 meters higher than today and the poles were 10 degrees Celsius hotter. During this epoch, forests grew along the shores of the Arctic Ocean and coral reefs were almost wholly absent.

"At the beginning of industrialization the concentration of CO2 was just 280ppm," said Rajendra Pachauri, chair of the Intergovernmental Panel on Climate Change (IPCC). "We must hope that the world crossing this milestone will bring about awareness of the scientific reality of climate change and how human society should deal with the challenge."

Concentrations of carbon dioxide fluctuate depending on the season with May usually showing the highest numbers, followed by a slight dip. However, scientists say that concentrations are expected to hit 400ppm more frequently over the next few years, until eventually concentrations will remain above the milestone until the world starts slashing emissions and decades after (carbon stays in the atmosphere for 50-200 years). Last year, concentrations actually hit 400ppm, but that was only in portions of the northern hemisphere. While scientists say that hitting 400ppm is largely a symbolic milestone, it's nonetheless illustrative of how much carbon has been pumped into the atmosphere in the last 150 years.

For most of human history, concentrations of carbon dioxide fluctuated between 180ppm and 300ppm. But the Industrial Revolution led to widespread burning of fossil fuels for energy, which released a deluge of carbon into the atmosphere. Additional carbon was emitted by the destruction of forests and other ecosystems. These emissions have raised global temperatures by about 0.8 degrees Celsius (1.4 degrees Fahrenheit) since the Industrial Revolutions leading to melting glaciers, sea level rise, vanishing Arctic sea ice, species migrations, and increases in extreme weather such as droughts and floods.

Hurricane Sandy storm surge on the New Jersey shore. Research shows that while climate change may not cause more hurricanes overall, it's likely to lead to increasingly intense hurricanes. Rising sea levels also contribute to the damage inflicted by hurricanes such as as Sandy. Photo by: Master Sgt. Mark C. Olsen/U.S. Air Force/New Jersey National Guard.
Hurricane Sandy storm surge on the New Jersey shore. Research shows that while climate change may not cause more hurricanes overall, it's likely to lead to increasingly intense hurricanes. Rising sea levels also contribute to the damage inflicted by hurricanes such as as Sandy. Photo by: Master Sgt. Mark C. Olsen/U.S. Air Force/New Jersey National Guard.

"Hundreds of billions of tons of fossil-fuel pollution have poisoned our climate, bringing to our world increasingly extreme floods, droughts, and wildfires," Brad Johnson, campaign manager with Forecast the Facts said in a statement. "We must respond with urgent resolve to end this uncontrolled experiment on our only home."

Globally, nations have pledged to keep temperatures from rising above 2 degrees Celsius (3.6 degrees Fahrenheit), however pledges and action to date have not succeeded in cutting global greenhouse gas emissions which continue to rise year-after-year. Both the World Bank and the International Energy Agency (IEA) have warned that if business-as-usual continues, the world is headed towards a total climate catastrophe, devastating coastal cities, global agriculture, and leading to mass extinction. Some scientists have even warned that global warming could take down human civilization as we know it.

"We're in new territory for human beings—it's been millions of years since there's been this much carbon in the atmosphere," said Bill McKibben, founder of 350.org, which campaigns for the world to move the dial on carbon concentrations down to 350 ppm. "The only question now is whether the relentless rise in carbon can be matched by a relentless rise in the activism necessary to stop it."



the Muenster yellow-toothed cavy
Failed rains in Somalia in 2011 left carcasses of dead sheep and goats across the landscape. The failed rains, combined with instability, caused a famine that killed over a quarter of a million people. Research has shown that warming temperatures in the ocean may be increasing the chances of failed rains in East Africa, worsening droughts and food insecurity. Photo by: Oxfam East Africa/Creative Commons 2.0.













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CITATION:
Jeremy Hance
mongabay.com (May 11, 2013).

A new world?: carbon dioxide concentrations in atmosphere hit 400 ppm.

http://news.mongabay.com/2013/0511-hance-400-ppm.html