Heat is on to solve the global climate crisis

Kick the anti-scientific propaganda into touch. People, as well as nature, are the cause of some extreme weather events in the past couple of years

Boats and a floating dock lie on the dry harbour at Lake Hefner in Oklahoma City as drought continues to be a problem across the state. Sue Ogrocki / AP Photo
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Climate scientists have for years been warning the world the heavy use of fossil fuels - coal, oil and natural gas - threatens the globe with human-induced climate change.

The rising atmospheric concentration of carbon dioxide, a by-product of burning fossil fuels, would warm the planet and change rainfall and storm patterns and raise sea levels, they said. Now those changes appear in every direction, even as powerful lobbies and propagandists try to deny the what many believe is the truth.

In recent weeks, the United States has entered its worst drought in modern times. The states in the Midwest and the Plains, the country's breadbasket, are baking under a severe heatwave with little relief in sight.

Halfway around the world, Beijing has been hit by the worst rains on record, with floods killing many people. Japan is similarly facing record-breaking torrential rains.

Two of Africa's impoverished drylands - the Horn of Africa in the east and the Sahel in the west - have experienced devastating droughts and famines in the past two years. The rains never came, causing many thousands to perish, while millions face starvation.

Scientists have given a name to our era, the Anthropocene, a term built on ancient Greek roots to mean "the human-dominated epoch" - a new period of the Earth's history in which humanity has become the cause of global-scale environmental change. Humanity affects not only the Earth's climate but also ocean chemistry, the land and marine habitats of millions of species, the quality of air and water, and the cycles of water, nitrogen, phosphorus and other essential components that underpin life.

For many years, the risk of climate change was widely regarded as something far in the future, a risk perhaps facing our children or their children. That threat would, of course, have been reason enough to act. Yet now we understand better that climate change is also about us, today's generation.

We have already entered a new and very dangerous era. If you are a young person, climate change and other human-caused environmental hazards will be major factors in your life.

Scientists emphasise the difference between climate and weather. The climate is the overall pattern of temperature and rainfall in a given place. The weather is the temperature and rainfall in that place at a particular time. As the old quip puts it: climate is what you expect; weather is what you get.

When the temperature is especially high, or rains are especially heavy or light, scientists try to assess whether the unusual conditions are the result of long-term climate change or simply reflect expected variability. So, is the current US heatwave (making this the hottest year on record), the intense Beijing flooding, or the severe Sahel drought cases of random bad weather, or the result of long-term, human-induced climate change?

For a long time, scientists could not answer precisely. They were unsure whether a particular weather disaster could be attributed to human causes rather than to natural variation.

They could not even be sure they could detect whether a particular event (such as a heavy rainfall or a drought) was so extreme as to lie outside the normal range.

In recent years, however, a new climate science of "detection and attribution" has made huge advances both conceptually and empirically.

Detection means determining whether an extreme event is part of usual weather fluctuations or a symptom of deeper, long-term change. Attribution means the ability to assign the likely causes of an event to human activity or other factors. The new science of detection and attribution is sharpening our knowledge - and also giving us even more cause for concern.

Several studies in the past year have shown scientists can detect long-term climate change in the rising frequency of extreme events - such as heatwaves, heavy rains, severe droughts and strong storms.

By using cutting-edge climate computer models, scientists are not only detecting long-term climate change but also are attributing at least some of the extreme events to human causes.

The past couple of years have brought a shocking number of extreme weather events all over the planet.

In many cases, short-run natural factors rather than human activity played a role. Yet, even after carefully factoring in such natural year-to-year shifts, scientists are also finding several recent disasters probably reflect human-caused climate change as well. Human-caused warming of the Indian Ocean probably played a role in the severe drought last year in the Horn of Africa, which triggered famine, conflict and hunger.

The evidence is solid and accumulating rapidly.

Humanity is putting itself at increasing peril through human-induced climate change. As a global community we will need to move rapidly and resolutely in the coming quarter century from an economy based on fossil fuels to one based on cutting-edge, low-carbon energy technologies.

Human well-being, even survival, will depend on scientific evidence and technological know-how triumphing over shortsighted greed, political timidity and the continuing stream of anti-scientific corporate propaganda.

Jeffrey Sachs is the professor of economics and director of the Earth Institute at Columbia University. He is also special adviser to United Nations secretary-general on millennium development goals. The opinions expressed here are his own.

* Project Syndicate