Climate Change and Consequences

Even when climate changes slowly, in response to gradual centuries- or millenia-long cycles, species died out and civilizations collapsed.

The overwhelming consensus of climate scientists is that increased greenhouse gases in the atmosphere — particularly carbon dioxide (CO₂) — are transforming global climate. While it is true that CO₂ levels have varied over time, there is compelling evidence that current trends are both unprecedented and man-made.

Scientists have been able to reconstruct several millennia worth of atmospheric records by examining ice cores drawn from miles-deep ice sheets.¹ These records show a constant fluctuation of CO₂ levels, ranging from roughly 200 parts per million (PPM) to roughly 300 PPM. Over an ice core record of 800,000 years, scientists have never found any levels significantly higher than 300 (PPM) — until now. In the 1950s, CO₂ levels were recorded above 300 PPM. They have risen consistently since, and are now approaching 400 PPM.²

Total carbon dioxide emissions doubled between 1900 and 1950. They increased nearly four-fold between 1950 and 2000. Today, human activity is responsible for producing nearly 20 billion tons of carbon dioxide annually.³ Roughly forty-five percent of that total remains trapped in the atmosphere, while the remaining fifty-five percent is absorbed by plants, land, and oceans.⁴ There is no doubt that this increased level of carbon dioxide emissions is responsible for the dramatic increase in atmospheric carbon above levels recorded over the past million years.

The connection between carbon dioxide levels in the atmosphere — as well as the increase in other “greenhouse” gases which only exist due to industrial activity — and climate change is also increasingly a matter of settled scientific fact.⁵ Greenhouse gases trap heat in the atmosphere. This causes temperatures to rise globally, with the most extreme temperature increases at the poles. High temperatures reduce the extent of seasonal ice. In the northern hemisphere, the Northwest Passage from the Atlantic to the Pacific was ice free in 2006 for the first time in centuries.⁶ In the southern hemisphere, huge chunks of the Antarctic ice shelf have broken up and floated away over the past decade and there is increasing concern over the status of the massive West Antarctic ice sheet.⁷ Less ice results in less sunlight reflected back into space and more sunlight absorbed by now ice-free expanses of land and sea.⁸ This promotes further warming. At this point, global warming is a self-reinforcing process, a vicious cycle that threatens to transform the earth’s climate dramatically.

The earth’s climate has undergone several major transformations in its history. But for the most part, change has been gradual enough for the planet’s creatures to adapt over time. Animals migrated to more welcoming climates and plants adapted and spread as the environment changed. But even these broad adaptations were marked by tremendous destruction. Climate change throughout history has been a significant force in the expansion and extinction of species.⁹ Noting that the climate has changed in the past is not a source of comfort, but rather a warning about the fragility of our reliance on an interconnected web of climate-constrained habitats.

Indeed, even within the historical record, there are numerous instances of climate change leading to massive political upheaval.¹⁰ Many scholars attribute the movement of the Huns and the Mongols to changes in the climate of the Eurasian steppes. The Mayan civilization collapsed under the stress of climate change, as did Native American civilizations in the American Southwest.¹¹

Even when climate changes slowly, in response to gradual centuries- or millennia-long cycles, species died out and civilizations collapsed.

But now we live in a world of rapid climate change due to human activity. And we live in a world with more people than ever. The consequences of the best case assumptions are dire, of the worst, they are catastrophic.