The carbon tax (in Australia) starts on July 1 this year, so there’s some tidying up to do around the edges — appointments, financing, regulations — and then a big tick next to the climate policy box on the cabinet whiteboard. Minister Greg Combet has already taken on the additional portfolios of industry and innovation.
If only. A barely reported new study on Earth’s energy imbalance from NASA climate chief James Hansen and his research team contends that, far from answering the climate challenge, we have constructed “a Faustian bargain”.
The new NASA study (and science brief) reaffirms that increased levels of greenhouse gases caused by human activity — and not changes in solar activity — are the primary force driving global warming. With new calculations of the Earth’s energy imbalance, the study finds the planet’s surface continued to absorb more energy than it returned to space, despite unusually low solar activity between 2005 and 2010.
The study uses improved measurements from free-floating instruments to calculate the amount of heat that has been absorbed by the world’s oceans, and thus refines understanding of how heat and energy imbalances are distributed in the climate system. And that’s where news becomes more sobering.
One conclusion of the study is that “the overall cooling effect from aerosols could be about twice as strong as current climate models suggest”.
So what’s the big deal? Human activity modifies the impact of the greenhouse effect by the release of airborne particulate pollutants known as aerosols. These include black-carbon soot, organic carbon, sulphates, nitrates, as well as dust from smoke, manufacturing, wind storms, and other sources. Aerosols have a net cooling effect because they reduce the amount of sunlight that reaches the ground and they increase cloud cover. This is popularly known as “global dimming”, because the overall aerosol impact is to mask some of the warming effect of greenhouse gases.
Hansen’s new study estimates this aerosol “dimming” at 1.2 degrees (plus or minus 0.2°), much higher than previously figured. Aerosols are washed out of the atmosphere by rain on average every 10 days, so their cooling effect is only maintained because of continuing human pollution, the principal source of which is the burning of fossil fuels, which also cause a rise in carbon dioxide levels and global warming that lasts for many centuries.