Atmospheric carbon dioxide hits 400 ppm, so why should we care?

New research suggests the planet is heating up, possibly to a level it last saw 3.6 million years ago during the middle Pliocene. This announcement comes as scientists announce that CO2 levels have now reached 400 parts per million, a symbolic threshold.

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LOS ANGELES, CA (Catholic Online) - The last time the planet had this much CO2 in the atmosphere was 3.6 million years ago during the middle Pliocene era. The planet was free of arctic ice and trees grew in the across the region.

Sediment cores taken from the Russian lake El'gygytgyn reveal fossil pollen in the lake from Douglas firs and hemlock, suggesting the icy area was once covered with trees some 3.6 million years ago when it was much warmer than today.

A team of international researchers brought the cores up in 2009 and the study was co-authored by researchers Julie Brigham-Grette and Pavel Minyuk. Their findings help confirm the belief that the arctic was once a lush location.

Such is the world we might expect to see if global warming is happening. Indeed, satellite data also suggest the tundra is defrosting and green vegetation is creeping north as the snow and ice retreat.

This raises two questions, which are commonly asked.

First, if the planet has been so warm before, what's to say the current warming trend isn't natural? And second, if the planet has survived such temperatures before, then why the alarm?

Despite the seemingly benign effects of warming, climate researchers fear that the planet is warming much more quickly that it would if the warming were natural in origin. This rapid warming harshly impacts both natural habitats and human societies.

Humans are unquestionably introducing more CO2 into the atmosphere than would enter it by natural means, with the understood exception of singular, distinct events such as major volcanic eruptions. This input is a natural consequence of human mass consumption of natural resources. According to most climatologists, this extra CO2 is driving the recent warming trend, which the planet has noticeably experienced over the past several decades.

This warming trend is manifesting itself in various ways, including the loss of arctic ice, the spread of greenery into arctic regions, and the rise of sea levels. Although aggregate temperature changes appear to have increased more slowly than feared during past decade, scientists believe this slowdown is only because the planet is absorbing additional heat in the oceans. This only grants a temporary reprieve from the accelerated warming of the recent past.

Although the loss of Arctic ice and the greening of the north isn't likely to be fatal to humanity, it is likely to be very disruptive. Natural selection, which is the means by which organisms adapt to changes in their environment, cannot keep pace with the rapid speed of today's environmental changes. This is leading to major extinctions and loss of wildlife that would otherwise have much more time to adapt.

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Human societies are also facing disruption as sea levels rise.

Regardless of the facts of the case, and regardless of what happens next, humanity will survive this transition just as it has survived similar major environmental shifts in the past. Humanity survived the last ice age, the desertification of the Sahara and the Fertile Crescent, and it will survive this. But how well it copes remains to be seen. Great environmental shifts also brought disasters which collapsed the earliest civilizations. It remains to be seen if our technologically sophisticated, massively integrated, and curiously fragile modern civilization can survive the coming changes before us.

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