By Owen Hart

IS THE CURRENT CLIMATE CHANGE UNUSUAL COMPARED TO EARLIER CHANGES IN

EARTH’S HISTORY?

IS OUR CLIMATE CHANGING?

YESEVIDENCE THAT EARTH’S CLIMATE IS CHANGING

• The polar ice caps are melting

• Sea level is rising

• Extreme weather events

Artic Sea Ice in SeptemberMount Kilimanjaro in February

1993

2000

WHAT COULD BE CAUSING THESE CHANGES?• POLLUTION

• Cars and factories emitting carbon dioxide

CARBON DIOXIDE CONCENTRATION: THEN AND NOW• Then (over the past 650,000 years)

• The concentration varied between a low of 180 ppm and the highest being 300 ppm

• Now (last decade)

• Concentration of CO2 has rapidly increased and is now at 379 ppm

It usually takes about 5,000 years for an 80 ppm increase in CO2 concentration

Rise in the temperature matches the rise in CO2 concentration after 1950

CLIMATE: THEN AND NOW• Climate change is a gradual process

• Then:

• Medieval times were warm, and in the 17 th 18th and 19th century it began to cool

• Now:

• Global temperatures are increasing at a very rapid rate

CONCLUSION

It is not unusual for the climate to change, but how fast and why it is changing is what is

unusual.