Complex sentence: Fourier recognized that the atmosphere transmitted visible light efficiently, that the earth's surface absorbed light and emitted infrared radiation in response, and that the atmosphere did not transmit infrared efficiently, which therefore increased surface temperatures.
Split into simpler sentences: Fourier recognized that the atmosphere transmitted visible light waves efficiently to the earth's surface. The earth then absorbed visible light and emitted infrared radiation in response, but the atmosphere did not transmit infrared efficiently, which therefore increased surface temperatures.