There are no Steps! It is Constant Warming By Golly

As greenhouse gases change the chemical composition of the atmosphere, the stratosphere will cool

While the average global surface temperature rises.  There are no step changes in climate, only the constant warming due to CO2 that threatens to destroy the world as we know it.  Trust us, we are scientists.

http://www.realclimate.org/index.php/archives/2004/12/why-does-the-stratosphere-cool-when-the-troposphere-warms/