Make no mistake – climate change will hit us hard. We need to clean up the mess before it is too late

Unmitigated climate change will hit global infrastructure hard and test the limits of our way of life.



The recent cold spell united red and blue states: not in their interpretation of the event, but in their affliction. Weather can hit our fragile societies much harder than we care to admit.

No single weather extreme can be unequivocally attributed to global warming. But physics can say something about the big picture before the small events that form the big picture have occurred; and it says that extreme weather is likely to intensify.

On Thursday, the Intergovernmental Panel on Climate Change officially released its latest assessment of the scientific basis of anthropogenic climate change, providing the huge body of science that support the much debated summary for policymakers agreed by the 194 governments some weeks earlier.

For the first time, future climate was not merely projected for the 21st century. About 20 climate models from around the world were used to look beyond the year 2100. They show that if greenhouse gas emissions continue to rise as they have done in the past, the Earth will warm by more than 10C and it won't stop there.

Yet this is not going to happen. Not because the physical models are wrong. They are built on fundamental laws of nature that we rely on in our every-day life, laws that were established more than a hundred years ago and that have been tested in countless laboratory experiments. For more than a decade, different models project practically the same temperature ranges for the same greenhouse gas emissions. So those who want to make the world believe that climate models are bad in projecting the temperature of our planet are wrong.

Still, a warming of our planet by 10C, as predicted by some models, is not going to happen – simply because the underlying assumption of these projections is that there will be an industry around that can produce further emissions of that magnitude. But climate change will interfere with our fragile economic supply chains through unanticipated weather extremes. Whether this might reduce our industrial emissions is hard to say.

Initially a perturbation of our economic flows is likely to increase emissions because the loss will need to be compensated. But it seems inevitable that there will be a limit. A limit beyond which we cannot clean up the mess quick enough before the next hurricane makes land fall. When this limit is reached emissions might decline – but not for the good of humanity.

When climate scientists started to investigate the impacts of climate change, they did what scientists have always done: we sought the hardest problems that we considered solvable and went for them. In the case of climate change this led us to investigate gradual changes in large scale climate variables such as globally averaged precipitation or the monthly mean temperature of a continent.

But weather extremes are much harder to predict and so we did not. Such an approach is actually very common in science. In physics for example, people invented the theory of relativity and quantum physics rather than solving the turbulence problem which affects our every-day life whenever we drive a car or ride a bike. The world of the atoms and that of the remote universe posed solvable problems compared to the small-scale chaos that develops behind every car and every airplane.

Climate change, however, does not allow for that kind of scientific luxury – focusing on outer space instead of local weather.

If unabated, climate change will simply come upon us. Just because we cannot compute the track of a hurricane does not mean that we will not have to face it. Events like this year’s heavy winter in the US, or typhoon Haiyan which destroyed parts of the Philippines a few months ago, show that it is the unanticipated extremes and their impact on our fragile infrastructure that we will have to worry about.

Such individual events might remain just as unpredictable in the future as they have been in the past, and they will continue to impact the global flow of goods, energy and information which connects economies across the planet and makes it one world. If Google’s headquarters in California were shut down by, say the lack of cooling during a heat wave, this would affect large and small business everywhere. If a severe storm was to hit the harbour of Hong Kong, the effects would not just be local. It would spread along the supply chains around the globe.

The temperature difference between the last ice age and our current warm period, which carried humankind into civilisation over the past 10,000 years, is less than 5C. This is about the amount of warming that we will have caused by the end of the century if we continue as we have done in the past. Only we are doing it about one hundred times faster than nature did while trying to keep a highly efficient global economic network running.

The 2011 floods in Thailand surprised insurance companies around the world, because they disrupted Japanese production of hard drives and other computer essentials and led to shortages in Europe and the US. In 2010, an Icelandic volcano spitting dust into the air led to flight cancellation for two weeks – and were enough to push Europe to the edge of an economic deadlock. Not only major airlines were reported to be in economic trouble, the entire transportation system in Europe was in turmoil , shaking all economic and political processes in the European Union.

Societies do not need to be brought to the verge of starvation to slide into crisis. The social unrests we have seen in New Orleans after hurricane Katrina or more recently in Greece as a result of the financial crisis suggest that also seemingly stable countries are vulnerable to abrupt perturbations.

It is the unanticipated impacts on fragile infrastructures and supply networks that constitute the largest threat of global warming. While climate change is often considered to be a problem for the global poor and for fragile ecosystems, the impact of extreme events on the global economic network will test the stability of America as much as that of Europe.

No one knows where the limits of our adaptive capacity are, but a path towards 10C of warming will likely challenge these limits. The wall we are speeding towards may be hidden in the fog, but not knowing where it is does not make it vanish. The warnings provided by weather impacts on our society are quite clear. We can either take them seriously and turn around or find out the hard way.

• Anders Levermann is a professor at the Potsdam Institute for Climate Impact Research, and an IPCC lead author

