(this is one of many FAQ files found at Terry)

The Intergovernmental Panel on Climate Change released its third assessment report back in 2001. The report concluded that the panel of prominent scientists expected the earth’s average temperature to rise from anywhere between 1.4 to 5.8% by 2100. This is a significant conclusion, even at the lower level of the scale, not only for the future havoc this would wreak on the earth’s biosphere but as well the political and economic influence such a statement could have in the here and now. So where do these numbers come from? What authority and legitimacy do these predictions hold? The answers lie in the relatively new science of climate modeling.

What is climate modeling?

Climate modeling is science’s attempt to try and understand the earth’s complex climate system and all its inherent processes. Arguably its most important roles are to discern whether anthropogenic forcing is responsible for the current global warming trend and to predict future increases in the earth’s average temperature as green house gas emissions continue to rise. This is accomplished using mathematics as well as computational analyses.

Because the earth’s climate system is a complex entity, complicated equations and algorithms representing the multitude of factors that play a part in the energy flow in the system are needed. The atmosphere, the oceans, the cryosphere (ice covered regions), land surface (including vegetation) and wildlife all need to be taken into consideration. Then one needs to take into account the transfer of energy through processes such as convection, condensation, evaporation, reflection and radiation. Finally one needs to input data concerning the green house gas emissions created by humans and the radiation they absorb, components that are arguably at the root of global warming. Once all of these processes have been put into equation form they are fed through supercomputers that put it all together in an attempt to simulate as close to the real thing as possible. The results then need to be validated by comparing them to past climate information obtained through analysis of tree rings and sediment deposits, a process known as Paleoclimatology.

What are the different types of climate models?

Climate models can range from relatively simple one dimensional models that simulate particular processes within the system to highly sophisticated, fully interactive three dimensional models that try to mimic the climate system as a whole.

On the simpler end of the spectrum we have energy balance models. These one dimensional models aim to mimic both the global radiation balance and the latitudinal energy transfer, which is the transfer of energy from the equator to the poles. These processes are regarded as the two most important in determining the state of the climate.

Another type of model is the one-dimensional radiative-convective model. This type of model attempts to simulate energy transfers throughout the atmosphere. These models are most useful for looking at forcing sources within the atmosphere, like say volcanic activity. Two-dimensional Statistical-dynamical models combine the two approaches of the previous mentioned models. Scientists use such models to understand the transfer of energy horizontally and the processes that may directly interrupt that flow.

The most complex of models in use today are three-dimensional general circulation models (GCM’s). While simpler models provide little room for interaction amongst the various components involved in the broad climate scheme, these models are fully interactive and can mimic global scale processes such as the effect of land masses on atmospheric circulation. Individual GCM’s that represent particular processes such as the ocean and the atmosphere are then coupled to provide as realistic a simulation of the earth’s climate system as possible.

Why is climate modeling important?

Global warming is happening. Are we to blame or is it a natural warming trend? Is reducing our CO2 emissions going to have any effect on dampening this process or is it too late? How much is the earth’s temperature going to increase in the next century and will the earth be inhabitable for anything more than (as the story goes) cockroaches? Climate modeling has the potential to answer these questions. It is even more important given the influence the scientific community can and does have on government decision making. To combat global warming, tough decisions need to be made by policy makers that may involve sacrificing short term benefit for long term gain. Policy makers, though, are responsible for the well being of their constituents and will only make these tough decisions if they are given valid scientific evidence that shows the dire consequences of not acting now. This is what climate modeling is attempting to do.

Climate modeling can also be an important tool for trying to predict monsoon and rain activity in tropical areas. Severe weather phenomenon such as these can cause immense suffering both in terms of casualties as well as damage to agriculture and other important means of survival. This area is of particular importance to India which has an agriculturally intensive based economy. In the last few years an Indo-US Science and Technology Forum has been set up to increase cooperation between the different scientific communities of the two countries in particular in regards to weather and climate modeling.

What is Canada’s contribution to the field?

Canada first became involved in this field back in 1970. Their main base of operations, the Canadian Centre for Climate Modeling and Analysis (CCCma), is located in Victoria, British Columbia. The CCCma is actually only one of a dozen operations globally that are working on coupled models and have the distinction of being one of only four centers whose climate models have been used by the IPCC in their predictions on global warming.

Environment Canada also has a large supercomputer in Dorval, Quebec, home of the department’s weather centre. This computer is used to run its coupled models. With the ability to calculate 128 billion mathematical operations per second, this powerful machine allows their climate models to simulate three years of climate in a single day. Environment Canada is currently working on a third-generation coupled model.

Is climate modeling an effective tool for predicting future climate change?

An argument one often hears from opponents of the Kyoto protocol is that the science behind climate change is too uncertain and fuzzy to rely on for making policy decisions that could have such a huge impact on our economies. There is definitely a certain level of uncertainty behind climate modeling and predicting the climate’s future. The natural variability of the process is one area of concern as well as the possibility of unknown factors influencing the system. There is also the uncertainty over our ability to accurately predict future emissions of green house gases and aerosols. It is difficult to predict exactly how much CO2 the developing countries will emit as they try to catch up to the developed world. There is also uncertainty over how the biosphere will react to global warming, in particular in regard to carbon storage. As climate change progresses and forests spread into normally inhabitable tundra regions, there will be an increase in carbon storage but inversely trees will die in other areas where drought is rampant in turn increasing the carbon in the atmosphere.

According to Dr. Naomi Oreskes and her fellow scientists, climate models are too large and complex and describe way too many processes to be tested and validated accurately ensuring that all processes are precisely represented. Bruce Hewitson of the University of Cape Town would agree that the uncertainty inherent in climate modeling does make all models somewhat inaccurate but that depending on the model and its particular attributes there is a lot of useful information that can still be ascertained. From this viewpoint not just one model can be relied on to predict future climate but that results from a variety of different sources must be collated to paint as accurate a picture as possible of what the future holds.

What does the future hold for climate modeling?

As mentioned earlier climate modeling is a relatively young field of scientific research and problems regarding the validity of data obtained using such models is abound. The complex nature of the earth’s climate makes uncertainty inevitable and makes precisely controlled experimentation inherently difficult. More money and talent needs to be attracted to this field of research so that progress can continue towards increasing the validity and prediction ability of these models. Important issues still need to be tackled such as understanding how clouds react to increased levels of green house gases and increasing the resolution of models so that they can project for small regional areas. As well we need to work towards increasing our understanding of past climates which will aid in validating future predictions and, in turn, increase their credibility.

There are a lot of tough decisions to be made on the climate change front. The economic livelihood of a good portion of the earth’s population relies on the production and consumption of fossil fuels. Sacrifices may need to be made on both the individual and government level if we are to make any headway in reducing Co2 levels and mitigate the effects of global warming for future generations. The necessary changes will be much easier to implement if the science of climate modeling is able to reduce uncertainty to a minimum and attain a certain level of validity and credibility in the eyes of both policy makers and the general public.

(artwork by Arthur Kwan)