CBCnews

IPCC report reinforces climate change reality

bobmcdonald-190.jpgBy Bob McDonald, Quirks & Quarks

As the famous scientist Neils Bohr (and, supposedly, baseball manager Yogi Berra) once said, "Predictions are difficult, especially about the future." Well, this week, the Intergovernmental Panel on Climate Change (IPCC) had some predictions about the future of climate change, with the release of its 5th Assessment Report.

In general, the report reinforces, with greater confidence, the fact that the Earth is, indeed, warming at an accelerated rate and humans are responsible for more than half of that change, mostly by burning fossil fuels. The science behind these claims is actually very robust.

Here's how the process works.

The IPCC does not, as a group, do original research. Instead, its role is to gather together all research that has been published around the world and assemble it into a global report. In other words, it looks at science that has already been through the peer review process by the scientific community. Then, the IPCC's own report is sent out for peer review to hundreds of scientists from many different countries. So by the time the report comes out, the science has been through the rigours of peer review twice.

Since climate is the study of long-term trends (unlike weather, which is what happens outside your window every day), the researchers face the difficult task of trying to piece together the climate of the past and compare it to what they see happening today. They then run that information through super-computer models to project these trends into the future. The farther back in time we look, the fuzzier the picture of the climate becomes.

Records from satellites only go back a few decades, and weather records only a century or so. To get the picture of the very distant past, scientists rely on ice cores from glaciers, tree rings, marine deposits, the fossil record and whatever relics from the past they can find. The picture they get shows changes over long time periods, going back millions of years.

All these lines of evidence show that while the Earth has been warming naturally since the last Ice Age, the rate of warming has increased since the mid-1800s, when the Industrial Revolution began and we started burning fossil fuels.

Recently, there has been a lot of attention paid to the fact that the rate of the Earth's warming has slowed over the last 15 years, which is often used as evidence that the science of the IPCC is flawed.

In nature, systems seldom change from one energy state to another in a nice smooth curve, like the ones in scientific graphs. Change usually happens in steps, where warming happens quickly for a while, levels off a little or even decreases for a time, then steps up again in a saw-tooth fashion.

So, the overall trend is still upwards. That is why, despite the slowdown, the last three decades have been the warmest on record.

If the focus is only on the steps where the rate has slowed down, that is a short-term view. It's like saying, "Hey, the Titanic isn't sinking as fast as it was earlier. Don't worry about it!"

The climate of the Earth is also affected by much more than just the temperature of the air. If a large volcano erupts, the ash thrown into the atmosphere blocks sunlight and causes cooling. The oceans are absorbing a lot of the heat and they have their own episodic temperature changes - such as El Nino - which affect the temperature and weather of the air above.

Glaciers and ice caps continue to retreat, which changes the colour of the land and sea surface from white to dark. White ice reflects sunlight, dark land and water absorbs it, then turns it into heat. Melting permafrost releases methane, another greenhouse gas, from all the thawing organic matter that's been frozen for thousands of years.

So, the changes in the planet's climate are affected by many different factors in an extremely complex system. That's why climate scientists are always refining their estimates, as the mechanisms driving the climate are better understood.
 
The changes in the Earth's environment are not just seen by climate scientists. They are also apparent to biologists, oceanographers, ornithologists and many other branches of science that study the Earth's ecosystems.
 
Scientists can only report on what they see. The next and perhaps more difficult task is to convince politicians to do something to reduce our impact. Whether you believe the optimists, the pessimists, the skeptics or deniers about the future, think of it this way: No matter how much change is predicted for planet Earth, there are still very good reasons to get ourselves off the dirty, inefficient, air-clogging technologies that are at the root of the problem.  

There are other ways to keep ourselves warm, move from place to place and turn wheels - without burning fossil fuels. Let's just get on with it.