Top Climate Scientist Argues for 6 Percent Annual Reduction in Greenhouse Gasses by 2012


A recent paper by NASA’s premier climate scientist James Hansen calls for a 6% reduction in greenhouse gas emissions each year starting in 2012. Noting that current greenhouse gas levels have already caused dangerous levels of warming, Hansen is calling for urgent action now to stabilize the world’s climate.

Hansen noted that the .8 degree Celcius increase in global temperatures since 1900 has already resulted in a number of dangerous climate impacts. Increasingly rapid polar sea ice decline, increasing melt in Greenland and Antarctica, receding mountain glaciers, a 1-2 percent yearly decline in coral reefs, the movement of habitable climate zones northward or to higher elevations, the expansion of deserts and dry zones, increased drought, excessive heat and fires, and the increased frequency of mega heat waves like those in Europe in 2003 and Russia in 2010 are all current effects of human-caused global warming and increased greenhouse gasses.

This observation that world climate systems are already undergoing substantial stresses at an .8 degree temperature increase led Hanson to conclude that sustained warming above 1 degree C was an intolerable risk. Hansen noted that, to stabilize world temperatures at a safe level, massive CO2 emission reductions need to start in 2012 at the latest.

If Hansen’s plan of 6% annual reductions were enacted by next year, temperatures would stabilize at around 1 degree C warming for the next thirty years and then slowly begin to drop off. If emissions draw-downs were delayed another 8 years to 2020, world temperatures would exceed the dangerous threshold for an entire century. Waiting until 2030 results in temperatures above 1 degree C for the next 500 years.

Hansen notes that a prolonged period of global temperatures exceeding the 1 degree C limit will likely result in passing certain climate tipping points. The higher heat is, therefore, much more likely to create a runaway warming scenario precipitated by a series of events that, once started, are outside of the control of human beings to reign back.

A runaway warming would likely start with the melting of arctic sea ice. The reduced reflectivity of ice during the summer would then cause the oceans to warm. Warmer oceans would destabilize methane frozen on the ocean floor. A portion of these massive stores would reach the atmosphere, convert to CO2 and further warm the climate. Other methane stored in lakes and in permafrost would also be released. Rising temperatures would cause more water vapor to be stored in the atmosphere. Water vapor is a powerful greenhouse gas. The result would be further temperature increases. Finally, all the world’s ice at the poles would convert to water and water vapor adding fuel to the already vicious cycle.

Hansen’s study also noted that expensive methods designed to use technology to remove CO2 from the atmosphere would likely be less effective than envisioned. Hansen notes that the cost of removing 50 parts per million of CO2 from the atmosphere would reach 60 trillion dollars by the end of this century.

Hansen’s warning is that current warming needs to be kept to near or below 1 degree C and that warming be turned back as soon as possible. Prolonged warmth at or above that threshold results in a high risk of starting a feedback effect similar to the one described above. And if feedbacks kick in, the world will change drastically into a dangerous place humanity is not at all accustomed to.