Recommended Definitions of “Global Warming” And “Climate Change”

As discussed often in my posts; e.g.

What is Climate? Why Does it Matter How We Define Climate?

What is Climate Change?

Is Global Warming the Same as Climate Change?

there is lack of clarity in how these terms are defined. In today’s post, I offer the following short definitions:

Global Warming is an increase in the global annual average heat content measured in Joules.

Climate Change is any multi-decadal or longer alteration in one or more physical, chemical and/or biological components of the climate system.

The figure below (from NRC, 2005) schematically illustrates the Earth’s climate system 


Thus climate change includes, for example, changes in fauna and flora, snow cover, etc which persists for decades and longer. Climate variability can then be defined as changes which occur on shorter time periods.

Global warming involves the accumulation of heat in Joules within these components of the climate system, which is predominently the oceans, as shown in Table 1 in Levitis et al 2001.  The current use of the global average annual surface temperature trend to diagnose global warming involves only the two dimensional land, cryosphere and ocean surface.

As I wrote in

Pielke Sr., R.A., 2008: A broader view of the role of humans in the climate system. Physics Today, 61, Vol. 11, 54-55.

“Unlike temperature at some specific depth in the ocean or height in the atmosphere, where there is a time lag in the response to radiative forcing, no time lags are associated with heat changes, since the actual amount of heat present at any time is accounted for. Moreover, because the surface temperature is a massless two-dimensional global field while heat content involves mass, the use of surface temperature as a monitor of climate change is not accurate for evaluating heat storage changes. “

My recommendation is that the next IPCC assessment adopt these definitions for global warming and climate change.

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