OK so back the CO2 and CO2-e comparison. Global warming and the resultant climate change we see in the future is not about just CO2 (carbon dioxide) Many other gases are global warming – greenhouse gases.
In defining greenhouse gases for the greenhouse effect, i.e. the global warming impact in carbon dioxide equivalent terms (CO2-e), methane (CH4) and nitrous oxide (N2O) along with CO2 work together as a cocktail of elements and thereby increase the warming effect of carbon dioxide alone. So when referenced in global warming potential (GWP),(generally over a 100 year timeframe) Methane has around 25 times the global warming impact of carbon dioxide (CO2) So 1 metric tonne of methane released today would be 25 metric tonnes of carbon in related terms. Nitrous oxide (N2O) has a warming effect of 298 times that of carbon dioxide. 1 tonne of Nitrous Oxide is equal in its global warming potential (again using a 100 year reference term) of 298 metric tonnes of CO2.
It is presently reported we are at around 455 – 465ppm in CO2-e terms of atmospheric concentrations. These CO2-e greenhouse gases are now increasing at an exponential rate and it is considered will continue to do so into the future.
There are many sources of methane release. These include but are not limited to emissions from livestock (a dairy cow will contribute 1.5 tonnes CO2-e per year) methane releases from landfills from the break down of organic waste, from mining operations such as coal mining and other geological deep formations, volcanic mud eruptions as an example, and the very big current concern; from thawing peat bogs on land in the northern latitudes of Siberia & Alaska (the West Siberian peat bog alone has an estimated 70 billion tonnes of stored methane- equal to 1,750 billion tonnes of CO2 or to put it another way 225ppm of CO2) (if this were to be added to the present ppm levels we would rocket to 610ppm). Another growing source of releases is from methane clathrates now thawing in waters in the previously frozen offshore Arctic sea bed. (when released to the surface 1 cubic metre of methane clathrates releases 164 cubic metres of methane) It is now suggested the Arctic will be ice free in summer by 2011 to 2015. It would be wise for us to start counting these inevitable releases into our projections.
Nitrous Oxide N2O is considered to be the fourth largest contributor to the greenhouse effect behind carbon dioxide, methane and water vapour (water vapour in a warmer world will rise). Nitrous Oxide too, is released from coal mining and the burning of coal for energy generation, steel manufacture and other industrial processes. It is also created in bushfires which in a warmer world are anticipated to become more prevalent. Thr recent bushfires in Victoria in a 2 week period released the equivalent in emissions of those the country reportedly emits in a year.
So are we facing global warming potential on levels of CO2 at 385ppm or on CO2-e at 460ppm and will we face the future on just CO2 levels or on CO2-e levels?
Should the science community and our political leaders wish to think and talk in terms of the end of the century 100 years (outside their term of office) we might suggest they collectively start talking same and same; and talk in terms of CO2-e in global warming potential terms; as by 2050 we are most likely to be past 1000ppm in CO2-e terms and in a much warmer world and future for the planet.
We can now see where James Hansen from NASA may borrow the line from the Apollo 13 crew “Houston we have a problem”