Read here. IPCC climate models have an atrocious record of predicting climate conditions. A principal reason is that they were funded to prove that human CO2 emissions cause global warming, which meant they had to be designed to do so. As a result, the models were programmed to be overly sensitive to increases in human CO2 emissions, and programmed to ignore or minimize sensitivity to other variables, including solar activity. New EU research now reveals that the IPCC reports and its associated climate models underestimate solar impact by some 6 times (see paragraph 5 of linked page).
Shapiro et al. conducted an analysis using Beryllium 10 isotope records, neutron monitor data, combined with sunspot records to reconstruct a Total Solar Irradiance record that indicates solar forcing best explains past climate changes, including the modern warming.
"The variable Sun is the most likely candidate for the natural forcing of past climate changes on time scales of 50 to 1000 years. Evidence for this understanding is that the terrestrial climate correlates positively with the solar activity. During the past 10 000 years, the Sun has experienced the substantial variations in activity and there have been numerous attempts to reconstruct solar irradiance. While there is general agreement on how solar forcing varied during the last several hundred years – all reconstructions are proportional to the solar activity – there is scientific controversy on the magnitude of solar forcing...We derive a total and spectral solar irradiance that was substantially lower during the Maunder minimum than the one observed today. The difference is remarkably larger than other estimations published in the recent literature. The magnitude of the solar UV variability, which indirectly affects the climate, is also found to exceed previous estimates." [A. I. Shapiro, W. Schmutz, E. Rozanov, M. Schoell, M. Haberreiter, A. V. Shapiro, and S. Nyeki 2011: Astronomy & Astrophysics]