Peter Irvine

office: Browns
tel: +44 (0)117 331 7313 extension: 17313
fax: +44 (0)117 928 7878

Supervisers: Dr Dan Lunt and Dr Andy Ridgwell

Should we geo-engineer our future climate?

There is international consensus that `dangerous´ (meaning: unacceptably damaging and/or disruptive to society) climate change should be avoided. Depending on what one assumes `dangerous´ is, it has been estimated that such a point could be reached at a concentration of CO2 in the atmosphere of only 450 ppm. Currently, atmospheric CO2 is ~384 ppm and increasing at a rate of about 2 ppm yr-1. Without radical changes in energy generation and usage and global economies it seems likely that we will start to experience dangerous climate change before the 2nd half of this century.

As a result, there is increasing interest amongst scientists and policy makers in the potential for removing CO2 from the atmosphere and/or directly altering the energy budget of the climate system so as to reduce future peak greenhouse warming. CO2 may be removed and semi-permanently isolated from the atmosphere by locking it up in terrestrial biomass, pumping it into the deep ocean (either using ships or pipelines to transport captured fossil fuel CO2, or by enhancing the biological pump in the ocean via nutrient fertilization or increasing vertical mixing and nutrient supply), or injecting it into geological formations - all forms of `CO2 sequestration´. Proposed modifications of the energy budget of the climate system include: injection of sulphate aerosols into the atmosphere and construction of a space-based `sunshade´ situated at the Lagrange point (L1) between the Earth and the Sun - both designed to reduce solar insolation reaching the Earth´ surface, or modifying the surface albedo so that less incident sunlight is absorbed, either of the surface ocean (e.g., by placing floating polystyrene balls in the ocean) or land surface (e.g., changes in plant clover).

Many of these `geo-engineering´ schemes proposed to mitigate the degree of future climate change remain un-quantified in their impact, and some are unlikely to be at all effective. All of them may give rise to unexpected climatic side-effects and hidden costs that render could them undesirable. Because of the urgency of the climate problem facing us there is a critical need to fully understand the role, if any, that `geo-engineering´ schemes might play in the future.

My research will involve a comprehensive analysis and inter- comparison of all major schemes currently proposed, together with additional schemes that might be devised as part of the research. I will use fully coupled general circulation models (GCMs) of the Earth´s climate system as well as interactive ocean and terrestrial carbon cycle models in order to simulate the impacts on global climate and carbon cycle of geoengineering in a future warming World.