A. A natural variation in climate

B. A result of human activity

C. Melting the polar ice caps

D. all of the above

There are 75 scientists that think 'B'. There are at least 31,000 that think 'A'.

E. An easy way to get free government money and live on easy street

D cheersh

D. all of the above.

Global ice extent is average, there is no extra melting http://arctic.atmos.uiuc.edu/cryosphere/...

Yes, what's your point?

Actually, any of these. "Some" is the keyword.

A. A natural variation in climate

B. A result of human activity

C. Melting the polar ice caps

D. all of the above