Neither sunspots nor TSI is determinative. It is essential to include the interaction between between solar output and galactic cosmic rays. If you have the patience, Henrik Svensmark's is the best presentation. Publications - FORCE MAJEURE The Sun's Role in Climate ... www.heartland.org › publications-resources › force-ma...Mar 6, 2019 —
Water vapor isn't just cloud cover. I heard that water vapor doesn't drive climate change, it only responds to and amplifies it. This is because as the planet warms, the air can hold more water, which warms the planet even more. You also need to calculate the climate forcing from water vapor and find how much of the recent warming it is responsible for.
Another thing is that scientists have actually looked at the heating from the sun compared to greenhouse gasses and found its climate forcing in watts per cubic meter is much lower than most other major factors. The sun simply hasn't changed enough in 150 years to cause the heating we are seeing.
Nir Shaviv has demonstrated the error of attempts to downplay solar influence. This is the contribution to the radiative forcing from different components, as summarized in the IPCC AR5. As you can see, it is claimed that the solar contribution is minute (tiny gray bar). In reality, we can use the oceans to quantify the solar forcing, and see that it was probably larger than the CO2 contribution (large light brown bar). Any attempt to explain the 20th century warming should therefore include this large forcing. When doing so, one finds that the sun contributed more than half of the warming, and climate has to be relatively insensitive. How much? Only 1 to 1.5°C per CO2 doubling, as opposed to the IPCC range of 1.5 to 4.5. This implies that without doing anything special, future warming will be around another 1 degree over the 21st century, meeting the Copenhagen and Paris goals. . . . My experience at the German Bundestag's Environment Committee in a pre-COP24 discussion
No, the feedback is negative because temperature affects evaporation rate far more than water vapor content. So cloudiness and precipitation increase faster than temperature, and cloud reduces temperature. Effectively none, because there was already so much water vapor in the air. The effective is logarithmic, and the difference in the atmosphere's water vapor content is so small that the effect on temperature is immeasurable.
Because the effect of the sun on earth's temperature is related to the sun's activity, not its energy output. NO. That's KNOWN to be FALSE because SOMETHING caused all the previous century-scale Holocene warming episodes, and it is KNOWN FOR CERTAIN that it WASN'T CO2. DO YOU UNDERSTAND? The 20th century saw the highest sustained level of solar activity in several thousand years, which naturally returned the earth to more normal Holocene temperatures after the coldest 500-year period in the last 10,000 years -- which also coincided with the lowest observed solar activity. Again, that graph is simply a fabrication with no basis in empirical fact.
TSI was chosen as the only acceptable index of the sun's effect on the earth's temperature after it was determined that it was not strongly related to temperature.
It's explained in the link. ". . . although the IPCC will not admit so, we know that the sun has a large effect on climate, and on the 20th century warming in particular. In the first slide we see one of the most important graphs that the IPCC is simply ignoring. Published already in 2008, you can see a very clear correlation between sea level change rate from tide gauges, and solar activity. This proves beyond any doubt that the sun has a large effect on climate. But it is ignored. . . . Having said that, it is possible to actually model the climate system while including the heat capacity, namely diffusion of heat into and out of the oceans, and include the solar and anthropogenic forcings and find out that by introducing the the solar forcing, one can get a much better fit to the 20th century warming, in which the climate sensitivity is much smaller. (Typically 1°C per CO2 doubling compared with the IPCC's canonical range of 1.5 to 4.5°C per CO2 doubling). You can read about it here: Ziskin, S. & Shaviv, N. J., Quantifying the role of solar radiative forcing over the 20th century, Advances in Space Research 50 (2012) 762–776. . . ."
