Tom Miles of Reuters calls our attention to the announcement of World Meteorological Organization, WMO, that Northern hemisphere hits carbon dioxide milestone in April. The WMO said levels of CO2 hit 400 ppm for the first time in human history.
The 400 ppm level in the atmosphere, up 40 percent since wide use of fossil fuels began with the Industrial Revolution, is rapidly spreading southwards. First recorded in 2012 in the Arctic, it has since become the norm for the Arctic spring.
The WMO expects the global annual average carbon dioxide concentration to be above 400 ppm in 2015 or 2016. Rising concentrations of the heat-trapping gas raise risks of more heatwaves, droughts and rising sea levels.
"Time is running out," WMO Secretary-General Michel Jarraud said in a statement.
"This should serve as yet another wake-up call about the constantly rising levels of greenhouse gases which are driving climate change. If we are to preserve our planet for future generations, we need urgent action to curb new emissions of these heat-trapping gases."
This report asserts temperature have risen 0.8C (1.4F) but does not say over what duration, I will track this down, and amend this incomplete statement.
Almost 200 governments have agreed to work out a deal by the end of 2015 to slow climate change as part of efforts to limit the average temperature increase to two degrees Celsius (3.6 degrees Fahrenheit) above pre-industrial times.
Last month the U.N. Intergovernmental Panel on Climate Change warned that greenhouse gas concentrations, would have to be kept below a level corresponding to 450 ppm for CO2, to give us as fair chance of keeping average planetary temperature from rising more than 2C, an amount that will still have adverse impacts.
Once reaons carbon dioxide levels are such as concern is that it remains in the atmosphere for hundreds of years, so even if we were to completely ramp down emissions of new pollutants we will be stuck at those atmospheric levels for a long time. So we don't have our usual human option up waiting until we bump up against catastrophe before taking remedial action.
Tim Miles tells us that over the last 800,000 years, CO2 levels have varied between 180 ppm and 280 ppm.