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For years, climate scientists have been warning the world that the heavyuse of fossil fuels (coal, oil, and natural gas) threatens the world with human-inducedclimate change. The rising atmospheric concentration of carbondioxide, a byproduct of burning fossil fuels, would warmthe planet and change rainfall and storm patternsand raise sea levels. Now those changes are hitting in every direction,even as powerful corporate lobbies and media propagandistslike Rupert Murdoch try to deny the truth.
In recent weeks, the United Stateshas entered its worst drought in modern times. The Midwestand the Plains states, the country’s breadbasket, are bakingunder a massive heat wave, with more than half of the country under a droughtemergency and little relief in sight.
Halfway around the world,Beijing hasbeen hit by the worst rains on record, with floods killing many people. Japan issimilarly facing record-breaking torrentialrains. Two of Africa'simpoverished drylands – the Horn of Africain the East and the Sahel in the West – haveexperienced devastating droughts and famines in the past two years: the rainsnever came, causing many thousands to perish,while millions face life-threatening hunger.
Scientists have given a name to our era, the Anthropocene, a termbuilt on ancient Greek roots to mean “the Human-dominated epoch” – a new period of earth’s history in whichhumanity has become the cause of global-scale environmental change. Humanityaffects not only the earth’s climate, but also ocean chemistry, the land andmarine habitats of millions of species, the quality of air and water, and thecycles of water, nitrogen, phosphorus, andother essential components that underpinlife on the planet.
For many years, the risk of climate change was widely regarded assomething far in the future, a risk perhaps facing our children or theirchildren. That threat would, of course, have been reason enough to act. Yet nowwe 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 youngperson, climate change and other human-caused environmental hazards will bemajor factors in your life.
Scientists emphasize the difference between climate and weather. Theclimate 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 orlight, scientists try to assess whether the unusual conditions are the resultof long-term climate change or simply reflect expected variability. So, is thecurrent US heat wave (makingthis the hottest year on record), the intense Beijingflooding, or the severe Sahel drought a caseof random bad weather, or merely the result of long-term, human-induced climatechange?
For a long time, scientists could not answer such a question precisely.They were unsure whether a particular weather disaster could be attributed tohuman causes, rather than to natural variation. They could not even be surethat they could detect whether a particular event (such as a heavy rainfall ora drought) was so extreme as to lie outside thenormal range.
In recent years, however, a new climate science of “detection andattribution” has made huge advances, both conceptually and empirically. Detection means determining whether an extremeevent is part of usual weather fluctuations or a symptom of deeper, long-termchange. Attribution means the ability toassign the likely causes of an event to human activity or other factors. Thenew science of detection and attribution is sharpeningour knowledge – and also giving us even more cause for concern.
Several studies in the past year have shown that scientists can indeeddetect long-term climate change in the rising frequency of extreme events –such as heat waves, heavy rains, severe droughts, and strong storms. By usingcutting-edge climate models, scientists are not only detecting long-term climatechange, but also are attributing at least some of the extreme events to humancauses.
The past couple of years have brought a shocking number of extreme eventsall over the planet. In many cases, short-run natural factors rather than humanactivity played a role. During 2011, for example, La Niña conditions prevailed inthe Pacific Ocean. This means that especiallywarm water was concentrated near Southeast Asia while colder water wasconcentrated near Peru.This temporary condition caused many short-term changes in rainfall andtemperature patterns, leading, for example, to heavy floods in Thailand.
Yet, even after carefully controlling for such natural year-to-yearshifts, scientists are also finding that several recent disasters likelyreflect human-caused climate change as well. For example, human-caused warmingof the Indian Ocean probably played a role inthe 2011 severe drought in the Horn of Africa, which triggered famine,conflict, and hunger, affecting millions of impoverished people. The current US mega-drought probably reflects a mix of naturalcauses, including La Niña,and a massive heat wave intensified by human-caused climate change.
The evidence is solid and accumulating rapidly. Humanity is putting itselfat increasing peril through human-inducedclimate change. As a global community, we will need to move rapidly andresolutely in the coming quarter-century from an economy based on fossil-fuelsto one based on new, cutting-edge, low-carbon energy technologies.
The global public is ready to hear that message and to act upon it. Yetpoliticians everywhere are timid, especiallybecause oil and coal companies are so politically powerful. Human well-being,even survival, will depend on scientific evidence and technological know-howtriumphing over shortsighted greed, political timidity,and the continuing stream of anti-scientific corporate propaganda.
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