The nay-sayers admit the globe has warmed but deny it is the result of human activity. They say it is caused by the sun getting warmer. In fact it is quite likely that changes in the sun’s temperature do cause changes in the the Earth’s temperature. But that does not prove the current temperature increase is caused by the sun.
Starting in late 1978, NASA began monitoring the sun’s power output from space. This increased the accuracy of such measurement by more than 10 times and produce the first accurate record of Total Solar Irradiance (TSI), which is astro-speak for total solar power reaching the earth.
Sun spots, though cool, are indicators of solar storms which have hot spots, so when there are more sun spots the sun is hotter than usual. Sunspots go in 11 year cycle and so does the sun’s heat as can be seen above. But since the record began there appears to be no connection between solar heat and global temperature. The swings in solar heat at first appear to keep step with temperature, but the earth’s temperature gets ahead of the sun to the point where in 2000, the earth’s temperature hits a valley exactly when the sun’s temperature reaches a peak. Moreover, the solar ups and downs are huge compared with any possible trend, while the earth’s ups and downs are minor compared with its trend.
The consensus among astrophysicists studying this connection is that, while some (but not all) historical climate changes were probably significantly influenced by the sun, the present upswing is due mainly to human activity.