Let's talk plainly. The vast majority of world scientists agree that our global climate system is warming rapidly because of human activity. As we put more carbon dioxide and other greenhouse gases into the atmosphere, we experience higher air and ocean temperatures, widespread melting of snow and ice, rising sea levels, big changes in natural systems and other adverse global and regional impacts.

Worse yet, greenhouse gas emissions have a lag effect. If we stop putting these gases up there, it will still take many years for what is up there now to go away. Meanwhile, the earth will continue to get warmer and warmer for a long time before balance is restored. The sooner we start to solve the problem, the better off we will be. If we do not change our ways, the earth will change them for us.

This is not a natural cycle or minor trend. Human activity is causing the problem and raising a growing risk of serious consequences. Make no mistake about it. This problem needs more attention.

Since pre-industrial times, we have dramatically increased the atmospheric level of greenhouse gases (GHGs) like carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). More recently, this growth has accelerated very rapidly. From 1970 to 2004 alone, atmospheric levels of these gases rose 70%. Scientists studying ice cores tell us that these levels far exceed anything the earth has seen for many thousands of years. As the levels of these gases grow, the earth retains more energy from the sun and global temperatures rise steadily. It is a direct cause and effect relationship.

Global warming has already caused the seas to rise, made storms stronger and moved them in different patterns, raised air and water temperatures (affecting plants, wildlife, insects and disease), expanded the areas affected by drought, encouraged heavy rain and snow in other areas and made the oceans more acidic as they absorb carbon dioxide from the air. This latter effect may be the worst of all because acidic water can kill off marine shell forming organisms (like corals) and the fish and other species that depend on them for survival.

We need to move from denial and indifference to creativity and collaborative action. If we continue to fill the atmosphere with greenhouse gases at current or greater rates, we will cause further warming and make these negative changes even worse. Some of the impacts could be abrupt or irreversible, depending upon the rate and magnitude of the temperature change.

Since at the moment we have not agreed on any effective way to create global economic growth without putting these gases into the atmosphere, we all have some serious work to do if we want to avoid big problems later.