Carbon dioxide is an important greenhouse gas. It acts as a blanket, trapping the heat from the sun.

Atmospheric carbon dioxide has increased by more than 23% since the start of the industrial revolution and by 13% since 1958 alone. This increase is unprecedented in a climate record that scientists can push back 200,000 years.

SeaWIFS - a 5 year mission

But during the northern hemispheres spring carbon dioxide is removed from the atmosphere by growing plants.

Across the northern seas single-celled floating plants start multiplying just below the ocean surface. Together land and oceanic plants reduce the atmospheric carbon dioxide by about 2%

This year these plants are being watched from space by the SeaWIFS satellite that was launched last August. It contains a camera sensitive to the spectral signature of chlorophyll, the chemical used to harvest the energy of sunlight.

An algal bloom off Alaska

The latest SeaWIFS images show widespread so-called algal blooms, fed by nutrients washed into the sea from the land.

The satellite can provide a plant cover map of the entire Earth and can determine the concentration of the microscopic marine plants called phytoplankton.

SeaWIFS will continue monitoring. When the northern hemisphere experiences autumn the plants will die and carbon dioxide will be released back into the atmosphere.

Because there is less land in the southern hemisphere seasonal plant growth is less pronounced there.

Scientists are interested in how the plant carbon dioxide cycle will interact with the increasing level of the gas released into the atmosphere by mans activities.