It might be counterintuitive, but as the globe seems to warm, temperature readings indicate summer maximum temperatures are on the decline. However, at the same time, winter minimum temperatures are on the rise, so that the overall average has been an increase in temperature. Meanwhile, up in the stratosphere, the temperature has been cooling even as surface temperatures warm up. The reason for this is the destruction of ozone gases, which absorb ultraviolet radiation, which generates heat. The less ozone, the more UV radiation gets through the stratosphere, so it does not have as much of a chance to warm up. Records taken since 1979 show that three of the coldest stratospheric readings have been in 1997, 2000, and 2006.