Research has shown that air pollutants from fossil fuel use make clouds reflect more of the sun's rays back into space. This leads to an effect known as global dimming whereby less heat and energy reaches the earth. However, it is believed that global dimming caused the droughts in certain parts of the world where millions died, because the northern hemisphere oceans were not warm enough to allow rain formation. Global dimming is also hiding the true power of global warming. By cleaning up global dimming- causing pollutants without tackling greenhouse gas emissions, rapid warming has been observed and various human health and ecological disasters have resulted, as witnessed during the European heat wave in 2003, which saw thousands of people die. ______.