Climate Change: Fitting the Pieces Together

Past Climates

Graph of temperatures and CO2 concentrations for the past 800,000 years (not including today's values)

Certainly, temperatures in Earth's past have been higher (and lower) than today, and
CO₂ concentrations have varied considerably. At certain times, changes in the Earth's orbit caused warmer temperatures, which increased CO₂ and produced additional warming in a feedback process. But today, the CO₂ released by human activities is triggering the increase in temperatures.

What Do You Think?

Question

How does the 2008 concentration of CO₂ compare to the highest concentration observed during the last 800,000 years?

a) Higher than the highest peak (more than 300 parts per million atmospheric molecules [ppm])

b) About the same as the highest peak (about 300 ppm)

c) About the same as the lowest level (about 180 ppm)

d) In between the lowest and highest levels (about 240 parts per million)

The correct answer is a).

Please resume watching the video above to hear the explanation.

Graph of temperatures and CO2 concentrations for the past 800,000 years (including today's values)

The average 2008 CO₂ concentration recorded at Mauna Loa, Hawaii was 385.3 ppm. Compare that to the high value of 300 ppm found in the 800,000-year long ice core record. Not only is today's concentration higher, the increase is occurring much faster (over about a century) than past CO₂ spikes, which generally happened over several thousand years.
What makes all this worrisome is that we are pushing the system out of the range human civilization has adapted to. The last time the poles were this warm was about 125,000 years ago during the last period between ice ages. The warming we saw in the 20th century happened 10 times faster than the climb out of the last ice age.

Please make a selection.