Temperature, CO2 and Sea Levels move together

Sea levels, Carbon dioxide concentrations, and Global temperatures have moved together over the last 450,000 years.


The graphs show the movement over the last 420,000 years of:
. Sea levels (the blue line)
. Carbon dioxide concentrations in the air (the green line), and
. Global temperatures (the red line).

The carbon dioxide concentrations have fluctuated between about 180 and 280 parts per million (ppm) over this period of 420,000 years, but in the last 50 years, it has rocketed to above 410 ppm. (See the red circle on the green carbon dioxide graph.)  

The sea levels and temperatures have moved with carbon dioxide levels in the past.  This suggests that the recent increase in carbon dioxide will lead to large rises in sea level and temperature.

The graph shows five periods of high temperatures. We are living in one of those warm periods. During the previous warm period, about 120,000 years ago, the temperature was a few degrees warmer than at present, and the sea level rose about 8 meters higher than the present – and carbon dioxide levels were a lot lower than they are now.

The work of Hansen and Sato provided the basis of this graph

(John Englander: Oceanographer)

Glaciers in retreat:

Glaciers around the world are in retreat. The Taku Glacier in Alaska has been studied since 1946, and only now, in 2019, has it started retreating. Out of 250 alpine glaciers studied, this had been the only one not in retreat. Now there are none. At 1,500 metres thick, it’s one of the world’s thickest mountain glaciers, now retreating by up to 390 billion tons of snow and ice a year.

This is a big deal. Mighty glacier finally succumbs to climate change. (The Age: 8 Nov 2019)

Glacial altitude feedback loops

As you descend from the top of a mountain, the air-temperature normally increases. Now, some alpine glaciers are 1,500 metres thick and some Greenland glaciers are 3,000 metres thick. So, as these glacial surfaces drop, there are significant potential increases in air-temperatures at the glacier surface.

This temperature difference is the basis for a feedback dynamic that can amplify glacial retreat or growth. While this glacial altitude feedback loop is dominant:

  • a decrease in the altitude of the glacier’s surface increases the average temperature at the surface of the glacier,
  • this increases the melting of snow and ice on the surface,
  • this decreases the altitude of the glacier’s surface and closes the feedback loop.

This feedback loop is reversible, as if the glacier’s altitude increases, the average temperatures decrease.

The Extreme Ice Survey

The Extreme Ice Survey collects visual evidence of the impact of global warming on our planet, like time-lapse photos of the contraction of the glaciers.  Outside of the Antarctic, 95% of the world’s glaciers are retreating.

See the film “Chasing Ice”, produced in cooperation with National Geographic. It won an Emmy award as an outstanding nature program.

Also a TED talk by James Balog in July 2009

Related pages

Updated 10 Nov 2019