Sunday, January 29, 2012

Climate Change, Disbelief, and the Collision Between Human and Geologic Time by Peter Gleick

Geologic time scales are long – too long for the human mind to really comprehend. Over millions, and tens of millions, and hundreds of millions of years, the Earth has changed from something unrecognizable to the planet we see on maps, plastic globes, and photos from space. The Atlantic Ocean didn’t exist eons ago and it will literally disappear in the future as the continental plates continue to move inch by inch. A visitor from outer space millions of years ago would have looked down upon land masses and land forms unrecognizable today. As John McPhee notes in his book, Assembling California, “For an extremely large percentage of the history of the world, there was no California.” Or North America, China, Australia, Hawai’i, Mt. Everest, Grand Canyon, or any of the other landforms and natural symbols we think of as immutable.

Humans cannot relate to these changes. Our perception of time is short — measured in days, months, years, or decades, not millennia or eons. And our perception of the world around us is similarly driven by events with human time scales. Again, John McPhee:

 Nowhere is this collision of time scales more pronounced than in the current climate change debate. There are a variety of reasons why a few people still find the reality of human-caused climate change to be inconceivable. Leaving aside those who are unfamiliar with or ignorant of the science, those who simply shill for the fossil-fuel industry, and those who for political reasons must toe an ideological line that contradicts scientific conclusions, there remain some whose world view prevents

"The two time scales – the one human and emotional, the other geologic – are so disparate. But a sense of geologic time is the most important thing to get across to the non-geologist: the slow rate of geologic processes – centimetres per year—with huge effects if continued for enough years. A million years is a small number on the geologic time scale, while human experience is truly fleeting – all human experience, from its beginning, not just one lifetime. Only occasionally do the two time scales coincide. When they do, the effects can be as lasting as they are pronounced."

them from accepting that humans can influence something so vast and global as the climate. Coupled with the fact that the Earth’s climate fluctuates naturally, this group has never been able to accept the reality of human-caused climate change. For regular readers of the blogs of climate contrarians (or their comments on this and other essays on climate change), this sentiment will be familiar. Here are a few examples:

"I don’t deny that the climate changes, it’s been changing since there has been an atmosphere to change. And it’s common knowledge that the earth goes through cycles of climate, what is not known is the exact causes of these changes or cycles.

Observed climate changes since 1850 are linked to cyclical, predictable, naturally occurring events in Earth’s solar system with little or no help from us.

Global Warming, Global Cooling and Global Climate Change have been happening for millions of years – long before any possible human influence – Climate Change is natural and nothing new.

This is a manifestation of the collision that McPhee describes, the conflict of human and geologic time scales."

Climate does change naturally for reasons well understood by scientists. But it does so over thousands or tens of thousands of years – time scales so slow as to be imperceptible to humans. The causes of these natural climate changes are the cumulative result of tiny but cosmic changes, including incremental shifts in the orbit of the planet around our star, the tiny but real wobble of the Earth’s axis, and variations in the output of energy from the Sun. These natural factors lead to changes in the Earth’s climate. They cause the ice ages, and they cause the warm interglacial periods. But they happen slowly – in geologic time unseen, unperceived, and unfelt by humans. The peak of the last ice age was 20,000 years ago, long before human civilization existed. The next ice age isn’t expected to start for thousands of years and may not peak for tens of thousands of years, and who knows what kind of civilization will exist then.

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