CLIMATE CHANGE: What We Know and What We Don't Know Baased on a Presentation by Daniel L. Albritton, Director of NOAA Aeronomy Laboratory, during early 2001.

There is a natural Greenhouse Effect. It keeps the earth warmer than it would be otherwise.

Our planet’s atmosphere is composed of: 78% Nitrogen 78% Nitrogen 20% Oxygen 20% Oxygen *2% Water Vapor (*greenhouse gas) *2% Water Vapor (*greenhouse gas) *0.03% Carbon Dioxide (*greenhouse gas) *0.03% Carbon Dioxide (*greenhouse gas) Dry Air Composition: without water vapor

It warms up It warms upand... It emits infrared light (heat) It emits infrared light (heat) If an object is bathed in sun light... If an object is bathed in sun light...

Water Vapor and Carbon Dioxide have been part of our atmosphere for millions of years. They cause an average surface temperature of about 60 o F. They cause an average surface temperature of about 60 o F. Without them, the average would be about 5 o F. Without them, the average would be about 5 o F.

Greenhouse gases are increasing in the atmosphere because of human activities, and they are increasingly trapping more heat. - Carbon Dioxide has increased by 31% between 1800 and 2000, as measured by ice cores and air samples -Other gases have increased, too: Methane Methane Sulfur Sulfur What is the main cause of this increase?

There is a collective picture of a warming world, and human activities have likely contributed. -Global temperatures are up o F over the past 100 years -Which seems to be causing: Glacial retreat Snow-cover decrease Freeze-free periods lengthened Sea-level increased 4-8 inches

What could this mean for the Earth’s future?

Carbon Dioxide abundance will likely double before 2100 Predicted climate responses: Predicted climate responses: Global temperature rise of o F by 2100 Global temperature rise of o F by 2100 If so, this would exceed the natural changes over the past 10,000 years If so, this would exceed the natural changes over the past 10,000 years Sea level rise of inches by 2100 Sea level rise of inches by 2100

We live on a complex planet and we have imperfect knowledge; so, we can’t predict the future very well. We can’t predict a small area’s changes, but possibly a continent’s changes: We can’t predict a small area’s changes, but possibly a continent’s changes: Temperatures may increase Temperatures may increase as much as 40% above average as much as 40% above average Mid-continent soil may experience Mid-continent soil may experience increased drying increased drying A warmer world may mean heavier rains, A warmer world may mean heavier rains, with large differences between regions with large differences between regions It’s much tougher to call if hurricanes It’s much tougher to call if hurricanes will be more or less frequent will be more or less frequent

BOTTOM LINE - THE VAST MAJORITY OF SCIENTISTS AGREE: The issue is a real one The issue is a real one The first signs of human- caused climate change have likely occurred The first signs of human- caused climate change have likely occurred Some degree of further change appears inevitable Some degree of further change appears inevitable Exactly where (regions), when (rate of change), how much (magnitude) is hard to predict Exactly where (regions), when (rate of change), how much (magnitude) is hard to predict

The End *Remember your three Rs! Reduce, Reuse, Recycle! *Remember your three Rs! Reduce, Reuse, Recycle! What can you do? What can you do?