Now another milestone has been reached that looks even more threatening than the above one. On the morning of June 16, 2013, methane levels reached an average mean of 1800 parts per billion (ppb). This is 1100 ppb higher than pre-industrial peak levels.
Temperatures moved within lower and upper boundaries of respectively -8 and 2 degrees Celsius.
From a historic perspective, greenhouse gas levels have risen abruptly to unprecedented levels. While already at a historic peak, humans have caused emissions of additional greenhouse gases. There's no doubt that such greenhouse gas levels will lead to huge rises in temperatures. The question is how long it will take for temperatures to catch up and rise.