It’s true that climate science is uncertain. But all science is uncertain, and climate science claims are less uncertain than economics claims. It has a much better record of prediction. And uncertainty cuts both ways: the ‘uncertainty’ about the impacts of climate change mean that things could be much worse than we think. A Danish statistician named Bjorn Lomborg wrote a book called ‘The Skeptical Environmentalist’. He sometimes shows some interesting ‘skepticism’ about environmentalist claims, but he doesn’t show skepticism about claims about economic activity, or cost, or growth, or markets. These assumptions are accepted so completely that we don’t even know they are assumptions. But this is the opposite of a skeptical attitude or a scientific attitude. Science advances when people discover assumptions they didn’t know they held.

Science is work, it takes time, and because it is cumulative, there are many pieces that build on others. What the denialists do is take one piece out of context and present some (usually dubious) counterevidence or simple argument. They are usually wrong about the pieces they take on, but they also try to use some small piece to discredit the entire building. In a short time, it's impossible to present all of climate science. If I had a full hour I could not do better than Al Gore did in his film. But let me just present some elements of the science as it was taught to me. You can, and should, look into it further if you are interested. If you do, I think you will be able to convince yourself of its validity.

The climate story

The basic argument is this. The energy to warm the earth comes from the sun's radiation. Some of that is reflected straight back into space by clouds or ice (the reflectivity of the earth is called its albedo). Some of it reaches the earth's surface, raises the earth's temperature, and radiates out as heat. Some of that heat is, in turn, trapped by the atmosphere and returned again to the earth's surface. How much heat is trapped by the atmosphere depends on the composition of the atmosphere – different chemicals have different characteristic frequencies that they emit at. CO2 emits heat. So does CH4 (methane) and some other important gases. The atmosphere has increasing amounts of these gases because we keep burning fossil fuels. The gases eventually cycle out of the atmosphere and back to the surface of the earth, when plants grow for example, but we are emitting into the atmosphere much more and much faster than the carbon is returned to the earth's surface. The result is more heat in the atmosphere and higher temperatures, which, because the atmosphere and the climate are complex systems, have effects on everything else.

There is a carbon cycle. Carbon travels in a kind of equilibrium between the ocean and the earth's surface, plants and animals on that surface, into the atmosphere, and back. The processes that drive the carbon cycle have a lot to do with life. Plants take carbon from the atmosphere as they use energy from the sun to grow. Animals release carbon into the atmosphere when they breathe. When organisms die, a lot of the carbon in their bodies is released. But it can also be stored. Coal is ancient plant matter that has been stored. Oil is ancient plankton, from the ocean. These fossil fuels can be thought of as dead, trapped, concentrated solar energy.

Flannery quotes a scientist named Jeffrey Dukes at the University of Utah who concluded that 100 tonnes of ancient plant life is required to create four litres of petrol (about 1 gallon). Growing that much plant life takes a lot of years of sunlight. The equivalent of about 1 year’s fossil fuel use (1997) globally is 422 years of sunlight.

It takes a remarkable process to make oil, a really remarkable sequence of events over thousands of years. It is such a chance event that I want to describe it in detail. This is Flannery (pg. 76):

“The geological process for making oil is as precise as a recipe for making soufflé. First the sediments containing the phytoplankton must be buried and compressed by other rocks. Then, the absolute right conditions are needed to squeeze the orgnic matter out of the source rocks and to transfer it, through cracks and crevices, into a suitable storage stratum. This stratum must be porous, but above it must lie a layer of fine-grained, impervious rock, strong enough to withstand the pressures that [would shoot] the oil and gas into the air… and thick enough to forbid escape. In addition, the waxes and fats that are the source of oil need to be ‘cooked’ at between 100-135 degrees Celsius [water boils at 100 C] for millions of years. If the temperature ever exceeds these limits, all that will result is gas, or else the hydrocarbons will be lost entirely. As there is no cook tending the great subterranean ovens wherein oil is forged, the creation of oil reserves is the result of pure chance – the right rocks being cooked in the right way for the correct time, usually in a dome-shaped structure where a ‘crust’ overlies a porous oil-rich level that prevents the oil’s escape.”

It can't be replicated, which means our economy, based on it, is inherently unsustainable. But even if it could, our economy is also based on taking carbon that has been out of circulation, stored in the ground, for millions of years, and putting it into the atmosphere.

This changes the carbon cycle. To have an ecological world-view is to understand that everything is connected to everything else. So changing the carbon cycle changes the atmospheric temperature. It changes the hydrological cycle. It changes habitats for wildlife. It changes agricultural potentials and the amount and type of life different ecosystems can support. It combines with all the other kinds of toxins we release into the atmosphere, water, and land in complex and sometimes unpredictable ways. These changes are making parts of the earth, which are habitat for diverse life forms, unlivable. They are making parts of the world where millions of people live, unlivable. Let me not make the case for how serious the problem is, here. I refer you to Gore, or Flannery, or just the Intergovernmental Panel on Climate Change’s very conservative estimates. This presentation assumes you think the problem is very serious and must be solved quickly. The solution has an easy and a hard part.

The easy part of the solution

Two scientists from Princeton, Pacala and Socolow, published a paper in “Science” 2004 called “stabilization wedges”. The abstract of the paper is worth reading in full.

“Humanity already possesses the fundamental scientific, technical, and industrial know-how to solve the carbon and climate problem for the next half-century. A portfolio of technologies now exists to meet the world's energy needs over the next 50 years and limit atmospheric CO2 to a trajectory that avoids a doubling of the preindustrial concentration. Every element in this portfolio has passed beyond the laboratory bench and demonstration project; many are already implemented somewhere at full industrial scale. Although no element is a credible candidate for doing the entire job (or even half the job) by itself, the portfolio as a whole is large enough that not every element has to be used.”

The elements that Pacala and Socolow present include what I call non-solutions like ethanol fuel and nuclear power as well as things that have to happen like reducing reliance on cars and stopping deforestation. Ethanol is already contributing to rising food prices and hunger in Latin America. By taking agricultural land out of circulation to produce corn for ethanol that then goes in a car, we’re still emitting CO2. But we’re also feeding cars instead of people. And the energetics of ethanol are scandalous. Filling an SUV’s tank takes enough corn to feed a person for a year. The food system and farming is dysfunctional as it is, distorted because of energy inputs and ecological destructiveness, actually. But we are hoping to stabilize the climate in time to prevent millions from dying and being displaced because of floods and drought. We don’t want to do it in a way that threatens millions with mass starvation. Nuclear power has other problems. If there is no safe way of disposing of it, if there are small risks of unthinkably catastrophic events, it is irrational to keep incrementing these risks with new plants.

Another non-solution is carbon offsets. The idea here is that if you are going to emit CO2, you can purchase “offsets” somewhere else so that you can end up with a net carbon balance of zero – your money is taking up as much carbon as it is putting out. Most of these “offsets” have to do with planting trees. But trees need to be planted anyway, and there are a whole number of reasons why a tree should or shouldn’t be planted in a certain place. Is that agricultural land? Is it well-watered enough for growing trees? Is the tree useful habitat for wildlife, or would some other land use in that area make better habitat? Even more than this, forests have an equilibrium role in the carbon cycle. When they grow, they take carbon out of the atmosphere. When they die, they release it. Burning fossil fuels is not an equilibrium activity – we are taking carbon that’s been buried for millions of years, out of circulation for millions of years, and putting it into the atmosphere. Forests cannot be used as a substitute for reducing emissions.