A number of climate scientists have elected to take an advocacy position on policy actions with respect to climate change. It is titled the 2007 Bali Climate Declaration by Scientists

They include the statement

“The next round of focused negotiations for a new global climate treaty (within the 1992 UNFCCC process) needs to begin in December 2007 and be completed by 2009. The prime goal of this new regime must be to limit global warming to no more than 2 ºC above the pre-industrial temperature…”

They state that if

“this trend is not halted soon, many millions of people will be at risk from extreme events such as heat waves, drought, floods and storms, our coasts and cities will be threatened by rising sea levels, and many ecosystems, plants and animal species will be in serious danger of extinction.”

Unfortunately, these scientists link their advocacy position to the value of the global average surface temperature trend (i.e. of “no more than 2 ºC above the pre-industrial temperature“). This means that if the global average surface temperature cools or is not changing significantly in the next few years before substantial reductions in CO2 emissions are achieved, questions will be raised on their scientific acumen.

As reported on Climate Science, with respect to global warming (or cooling), it is the change in heat in Joules that is the proper metric, not the surface temperature. This is discussed, for example, in the weblogs,

http://climatesci.colorado.edu/2007/04/04/a-litmus-test-for-global-warming-a-much-overdue-requirement/

Recent data, which will be summarized soon on Climate Science, show that any accumulation of Joules since 2004 has been quite small, such that global warming has essentially stopped, at least for now.

This lack of warming is consistent with the absence of lower tropospheric warming since about 2003 (see Figure 7 in the RSS MSU data), and also reported on ICECAP.
http://climatesci.colorado.edu/2007/12/07/out-on-a-limb-the-2007-bali-climate-declaration-by-scientists/