E3G

Climate Change and Health

By Tom Burke

The scale of the challenge

Climate change is a bad problem that is getting worse. For the moment, it remains a manageable problem. But it is now clear that within the next few decades it will become an unmanageable problem unless we act decisively.

There is a very broad and deep consensus within both the scientific and policy making communities about the science of climate change. It is now accepted everywhere that human activities are changing the climate and at an unprecedented speed.

You will be hearing later in much more detail about the science of climate change, so all I will do at the moment is pick out some of the key numbers that illustrate the nature of the challenge we face.

Europe’s political leaders have been clear that a 20C rise above pre-industrial levels in global average temperature is the threshold of dangerous climate change. Jim Hansen, the climate scientist who has done most to alert the world to the dangers of climate change, and who you will be hearing from later, thinks that even this may be too high.

We have already observed a 0.70C rise since the beginning of the 20th Century. Such is the nature of the climate system that even if we were to halt all further emissions of greenhouse gases today, we would see another 0.70C before temperatures stabilised. You do not need to be a better mathematician than I am to agree that 1.40C is awfully close to 20C.

To be very confident of staying below this threshold – as Nick Stern pointed out in his landmark report – we need to keep the concentration of greenhouse gases to between 450 and 550 parts per million (ppm) carbon dioxide equivalent. That is the measured carbon dioxide plus the effect of all the other gases we are adding to the atmosphere expressed as their carbon dioxide equivalent.

At the lower end of that range our best estimate currently is that we would have only an evens chance of staying below 20C. At the upper end, the odds would be about 5 to 1 against staying below 20C. The concentration is now 425 ppm and rising at more than 2ppm every year.

Why climate change is different

There are three ways in which climate change is different from any other problem that humanity has ever faced.

The first is the sheer scale of the problem. Climate change threatens to undermine the prosperity, security and well being of literally every single one of the six and a half billion people on the planet.

No other problem does this. Millions of us are threatened daily by crime and conflict, but millions more lead lives of peaceful security. Many more of us lead poorly educated lives of unhealthy poverty but millions of others lead lives of well educated, healthy affluence. No-one will escape the consequences of a rapidly changing climate.

Second is the urgency. To have any chance of avoiding dangerous climate change total global carbon emissions have to peak within a decade and then decline rapidly. And they have to do this while meeting the rapidly expanding need for energy to fuel economic development. No-one will trade-off energy security for climate security so we must achieve both together.

Because agriculture, deforestation and land-use changes produce large carbon emissions which are very difficult to control this means, in effect, that we must develop a carbon neutral global energy system by around the middle of the century. This will require transformational changes in energy technologies on a scale that makes the Apollo or Manhattan Projects look unambitious.

Third, the nature of the climate system means we cannot afford policy failure. Humanity learns predominantly by trial and error. We make mistakes and then try again and again until we get it right. This often takes a long time. But for most problems the goal remains the same and we can keep moving towards it however erratically.

The long life of carbon in the atmosphere and the very large lag between stimulus and response in parts of the earth system mean that climate change is irreversible on human timescales. There is no rewind button. Once a given concentration of greenhouse gases is in the atmosphere we are committed to living with whatever climate it produces.

In other words, the goal we can reach changes with time. If our policy efforts fail, we cannot go back and try again for the same goal as it is no longer available. All that remains is the next worst option.