CLIMATE CHANGE: What We Know and What We Don't Know

CLIMATE CLIMATE CHANGE: CHANGE: What We What We

Know and Know and What We Don't KnowWhat We Don't Know

Baased on a Presentation by Daniel L. Albritton, Baased on a Presentation by Daniel L. Albritton,

Director of NOAA Aeronomy Laboratory, during early 2001.Director of NOAA Aeronomy Laboratory, during early 2001.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

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



Our planet’s atmosphere is Our planet’s atmosphere is composed of:composed of:

78% Nitrogen78% Nitrogen 20% Oxygen20% Oxygen *2% Water Vapor *2% Water Vapor

(*greenhouse gas)(*greenhouse gas) *0.03% Carbon Dioxide *0.03% Carbon Dioxide

(*greenhouse gas)(*greenhouse gas)



Dry Air Composition:without water vapor

It warms upIt warms up

and...and...

It emits It emits infraredinfrared light light (heat)(heat)



If an object is bathed in If an object is bathed in sunsunlight...light...

Water VaporWater Vapor andand Carbon DioxideCarbon Dioxide have been have been part of our atmosphere for part of our atmosphere for millions of yearsmillions of years..

They cause an They cause an average surface average surface temperature of temperature of about 60about 60ooF.F.

Without them, Without them, the average the average would be about would be about 55ooF.F.



Greenhouse gases are increasing in the Greenhouse gases are increasing in the atmosphere because of human activities, atmosphere because of human activities,

and they are increasingly trapping more heat.and they are increasingly trapping more heat.

--Carbon DioxideCarbon Dioxide has has

increased by 31% increased by 31% between 1800 between 1800 and 2000, as and 2000, as measured by ice measured by ice cores and air cores and air samplessamples

-Other gases have -Other gases have increased, too:increased, too:

MethaneMethane SulfurSulfur



What is the main cause of this increase?

There is a collective picture of a warming world, There is a collective picture of a warming world, and human activities have likely contributed.and human activities have likely contributed.

-Global temperatures are up -Global temperatures are up 0.7 - 1.4 0.7 - 1.4 ooF over the past F over the past 100 years100 years

-Which seems to be causing:-Which seems to be causing:

Glacial retreatGlacial retreat

Snow-cover decreaseSnow-cover decrease

Freeze-free periods Freeze-free periods lengthened lengthened

Sea-level increased 4-8 Sea-level increased 4-8 inchesinches

What could this mean for What could this mean for

the Earth’s future?the Earth’s future?



Carbon Dioxide abundanceCarbon Dioxide abundancewill likely double before 2100will likely double before 2100

Predicted climate Predicted climate responses: responses:

Global temperature rise of Global temperature rise of 2.5 - 10 2.5 - 10 ooF by 2100F by 2100 If so, this would exceed If so, this would exceed

the natural changes over the natural changes over the past 10,000 yearsthe past 10,000 years

Sea level rise of 4 - 35 Sea level rise of 4 - 35 inches by 2100inches by 2100



We live on a complex planet We live on a complex planet and we have imperfect knowledge; and we have imperfect knowledge;

so, we can’t predict the future very well.so, we can’t predict the future very well.

We can’t predict a small area’s We can’t predict a small area’s changes, but possibly a continent’s changes, but possibly a continent’s changes: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 dryingincreased drying

A warmer world may mean A warmer world may mean heavier rainsheavier rains, , with large with large differences betweendifferences between regions regions

It’s much tougher to call if hurricanes It’s much tougher to call if hurricanes will be will be moremore or or lessless frequent frequent



BOTTOM LINE - THE VAST BOTTOM LINE - THE VAST MAJORITY OF SCIENTISTS AGREE:MAJORITY OF SCIENTISTS AGREE:

The issue is a real oneThe issue is a real one

The first signs of human-The first signs of human-caused climate change caused climate change have likely occurredhave likely occurred

Some degree of further Some degree of further change appears change appears inevitableinevitable

Exactly Exactly wherewhere (regions), (regions), whenwhen (rate of change), (rate of change), how muchhow much (magnitude) (magnitude) is hard to predictis hard to predict



The EndThe End

*Remember your three Rs! *Remember your three Rs! Reduce, Reuse, Recycle!Reduce, Reuse, Recycle!





What can you do?What can you do?

Documents

CLIMATE CHANGE: What We Know and What We Don't Know