Those under the impression that climate change is advancing at a constant and predictable rate don't understand the true dynamics of the issue. The rate of increase of the carbon dioxide concentration in the atmosphere, the main driver of climate change, went from 0.75 parts per million (ppm) per year in 1959 to about 1.5 ppm each year through the 1990s, to 2.1 ppm each year from 2002 to 2012, and finally to 2.9 ppm in 2013.
The fear is that the ability of the oceans and plants to continue to absorb half the carbon dioxide human civilization expels into the atmosphere each year may have become impaired. That means more carbon dioxide is remaining in the atmosphere where concentrations are building at the fastest rate ever recorded in the modern era.
Permafrost across the most northern reaches of land on the globe wasn't expected the start melting until well into this century. Scientists were shocked to find gaping craters in Siberia where permafrost apparently is no longer permanent. It means carbon dioxide and methane--which absorbs about 80 times as much heat as carbon dioxide during its first 20 years in the atmosphere--will be unleashed from the melting permafrost much sooner than anticipated after being trapped for thousands of years. The release has the potential to speed up warming considerably.