A new study published in Geophysical Research Letters reinforces what what countless other studies in the past have found: That changes in the sun are not responsible for the global warming in recent decades.
Here is the abstract:
Although controversial, many observations have suggested that low-level cloud cover correlates with the cosmic ray flux. Because galactic cosmic rays have likely decreased in intensity over the last century, this hypothesis, if true, could partly explain 20th century warming, thereby upsetting the consensus view that greenhouse-gas forcing has caused most of the warming. The “ion-aerosol clear-air” hypothesis suggests that increased cosmic rays cause increases in new-particle formation, cloud condensation nuclei concentrations (CCN), and cloud cover. In this paper, we present the first calculations of the magnitude of the ion-aerosol clear-air mechanism using a general circulation model with online aerosol microphysics. In our simulations, changes in CCN from changes in cosmic rays during a solar cycle are two orders of magnitude too small to account for the observed changes in cloud properties; consequently, we conclude that the hypothesized effect is too small to play a significant role in current climate change.
For the record here are some other studies that have also found that changes in the sun are inadequate to explain the current warming trend:
- Solanki 2008: “Solar variability is unlikely to have been the dominant cause of the strong warming during the past three decades”
- Erlykin 2008: “We deduce that the maximum recent increase in the mean surface temperature of the Earth which can be ascribed to this activity is <14% of the observed global warming.”
- Lean 2008: “According to this analysis, solar forcing contributed negligible long-term warming in the past 25 years and 10% of the warming in the past 100 years.”
- Eichler 2008: “During the industrial period (1850-2000) solar forcing became less important and only the CO2 concentrations show a significant correlation with the temperature record.”
- Ammann 2007: “Although solar and volcanic effects appear to dominate most of the slow climate variations within the past thousand years, the impacts of greenhouse gases have dominated since the second half of the last century.”
- Lockwood 2007: “Here we show that over the past 20 years, all the trends in the Sun that could have had an influence on the Earth’s climate have been in the opposite direction to that required to explain the observed rise in global mean temperatures.”
- Foukal 2006: “The variations measured from spacecraft since 1978 are too small to have contributed appreciably to accelerated global warming over the past 30 years.”
- Usoskin 2005: “during these last 30 years the solar total irradiance, solar UV irradiance and cosmic ray flux has not shown any significant secular trend, so that at least this most recent warming episode must have another source.”
- Stott 2003: “most warming over the last 50 yr is likely to have been caused by increases in greenhouse gases.”
- Solanki 2003 “the Sun has contributed less than 30% of the global warming since 1970.”
- Lean 1999 “it is unlikely that Sun-climate relationships can account for much of the warming since 1970″.
- Waple 1999 “little evidence to suggest that changes in irradiance are having a large impact on the current warming trend.”
- Frolich 1998 “solar radiative output trends contributed little of the 0.2°C increase in the global mean surface temperature in the past decade.”
How many more studies debunking the denier notion that global warming is all due to the sun do we need for them to drop it as a reasonable explanation or the observed warming trend?
Of course the fact that no link between the sun and the current warming trend has been found hasn’t stopped deniers from blaming the sun, and grasping on the anything, no matter how absurd, to ‘prove’ it is all the suns fault.
And yet people wonder why I find the term skeptics wholly inadequate to describe the current crop of global warming deniers.