Overview

 … climate change is a permanent feature of planet Earth; any human impact that might be occurring is probably too small to discern against a background of natural variability (Singer, p. 118.

• There remain many uncertainties about how the climate system works, but scientists believe that the most important drivers of climate change are changes in (a) energy output from the Sun, (b) cosmic rays hitting the Earth which affects cloud cover, and (c) ocean currents. The processes by which the various forces affecting climate change interact and the net impact of these interactions are not well understood in precise detail, but the overall view seems clear.
• Basically the cause [of climate change] is related to the time scale under consideration:
  • Hundreds of thousands to million years – variations in galactic cosmic rays
  • Ten thousand to one hundred thousand years – changes in Earth orbit and motion
  • Decades to centuries- natural internal variability and solar variability (Singer, p. 105).

The Sun, an extremely under-appreciated driver of climate change

• Solar radiation as measured by the Active Cavity Radiometer Irradiance Monitor (ACRIM) total solar irradiance (TSI) composite shows a small upward pattern from around 1980 to 2000, an increase not acknowledged by the IPCC (Intergovernmental Panel on Climate Change) or incorporated into the models on which it relies…. Even small changes in the absolute forcing of the Sun could result in values larger than the much smaller predicted changes in RF [radiative forcing]  caused by human GHG [greenhouse gas] emissions (Singer, p.138. The Wikipedia definition of Radiative forcing is “the difference between solar irradiance (sunlight) absorbed by the Earth and energy radiated back to space. It is the scientific basis for the greenhouse effect on planets.”
• The conventional wisdom is that the variation of the solar constant, only 0.1 percent during the solar cycle, is too small to have an effect. But solar variations also produce indirect climate changes through solar corpuscular radiation (solar “wind”) sweeping past the Earth and the solar modulation of the flux of cosmic rays that affect cloud formation…. (Singer, p. 138).

Ocean Currents

• As with the impact of changes in energy from the Sun, the role of ocean currents – El Niño events, the PDO, North Atlantic Oscillation (NAO) and others – is still poorly understood. The satellite temperature data seem to reveal that El Niño  events were responsible for virtually all the temperature increase since 1979. PDOs have “cold” and “warm” periods while El Niño events last six to eighteen months (Singer, p. 182).

 Role of CO2

•  The current level of atmospheric CO2, about 416 ppm … in 2019, is about 130 ppm (46 percent) higher than the preindustrial level of 280 ppm (Singer, p.106).
•  CO2, so often blamed for changing the weather, is almost surely a minor player compared to natural processes (Singer, p.118).
• A sudden rise of nearly 0.2^o C [that] occurred between 1976 and 1978 [is] linked to a shift in ocean circulation. Upward shifts in temperature also occurred in 1997-98 and 2007-08, coinciding with changes in ocean currents. There is no known connection between ocean currents and the concentration of CO2 in the atmosphere (Singer, p. 106).
• Water vapor is responsible for most of the greenhouse effect. Without the presence of naturally occurring atmospheric GHGs like CO2 and especially water vapor, our planet would be a frozen wasteland with oceans covered by ice (Singer, p. 106).

Human contribution to the increase in atmospheric CO concentration

•  There is no dispute that levels of greenhouse gases … in the atmosphere have increased as a result of human activities. CO2 emissions have been increasing at about 0.5 percent per year …. (Singer, p. 106).
• Surveys show most scientists and meteorologists believe natural causes, not human influence, caused the majority of the temperature rise …. This does not argue that AGW (anthropogenic global warming) is absent, but that it is simply too small to be detectable …. (Singer, p. 110).
• … the human contribution of CO2 to the atmosphere that is thought to remain there for more than a short period (before being absorbed by the oceans and biosphere) is very small relative to natural processes, just 0.53 percent of the carbon entering the atmosphere each year…. Even small errors in the measurement of poorly understood exchange processes exceed the entire human contribution by orders of magnitude (Singer, p. 111). This fact alone should make a reasonable person find ridiculous the assertion that human activity is a main cause of climate change.