Predicting Global Warming

ENVS 110 (02-14-08)

Source: Commonwealth of Australia 2006, Bureau of Meteorology (ABN 92 637 533 532)http://www.bom.gov.au/climate/current/soi2.shtml (accessed 3/13/06)

http://www.cpc.noaa.gov/products/predictions/multi_season/13_seasonal_outlooks/color/page2.gif

How to Make Climate Predictions ?

• Climate Models– very simple energy balance models– more complicated general circulation models

(GCM’s)

– what to include– what to leave out– how do feedback’s work

Some Modeling Problems:

• generally low level of scientific understanding

• timescales involved

• high spatial resolution required to obtain “useful” results

• computationally expensive

GCM’s: The Hard-Core Approach

source:Hadley Center, The MET Office

“Low-Tech” Approach

• make very few assumptions about importance of forcings and feedbacks

• keep the math simple (relatively speaking)

• fast model, can do many runs, try many things

• can pick “best” result

• how to decide on “best” result?

source:Knuti et al., nature 2002

Comparison of two Approaches

Results of Climate Models

• all models predict a rise in temperature due to an increase in atmospheric CO2

• increase most severe in high latitudes– melting of polar ice caps– sea level rise– global cooling ?

• changes in precipitation, soil moisture

Results of Climate Modeling

From Mitchell et al., 2001

http://www.ucar.edu/news/releases/2006/ibm.shtml

So, who cares ?• societal concerns

(economic hardship)

• ecological concerns (survival of other species, ecosystems – why is

this a problem ?)

• ethical concerns(who will be affected the most?)

is global warming by definition a bad thing?

the underlying problem…

http://www.sustainablescale.org/AreasofConcern/Population/PopulationandScale/QuickFacts.aspx

population growth rates

http://upload.wikimedia.org/wikipedia/commons/2/27/Population_growth_rate_world.PNG