Myth often cited by global warming skeptics debunked
The reasons to disbelieve that humans are causing global warming are many and varied, skeptics say. For example: Natural factors such as long-term variations in solar radiation are causing the rise in worldwide average temperature. The urban heat island effect is skewing modern weather data, so the warming observed in recent decades isn’t real. And besides, not long ago experts all believed the Earth was cooling, not warming.
Actually, research has shown that many such ideas are bogus. While changes in solar output have slightly increased global average temperature since the beginning of the Industrial Revolution, the planet-warming effect of man-made greenhouse gases is about 20 times larger (