They point to the so - called ice ages, when the earth was supposedly much cooler than it is now; and in support of natural warming, they cite evidence that cold regions, such as Greenland, at one time supported vegetation that prefers warm areas.
Nad viitavad nn jääaegadele, mil temperatuur maakeral oli arvatavalt palju jahedam kui praegu; ning loodusliku soojenemise tõestuseks toovad nad näiteid selle kohta, kuidas külmadel aladel, nagu Gröönimaal, kasvas kunagi soojalembene taimestik.