by Judith Curry
So, what’s going on with the sun? The latest research was presented at the Nagoya Workshop on the Relationship between Solar Activity and Climate Changes.
WUWT has a post on this Workshop, which included presentations by Judith Lean and Leif Svalgaard, and Henrik Svensmark. Ithe following four presentations seem to be the most relevant to climate change:
- Judith LEAN: Variations in Solar Irradiance and Climate
- Leif SVALGAARD: The Long-term Variation of Solar Activity
- Martin BODKER ENGHOFF & Henrik SVENSMARK: Effects of Cosmic Ray Decreases on Cloud Microphysics
- Hiroko MIYAHARA: Effects of Galactic Cosmic Rays on Weather and Climate
Some highlights from Judith Lean’s presentation:
The following paper is referenced: Kopp and Lean (2011) GRL, summarizing total solar irradiance measurements from space and the nontrivial discrepancies in the baseline measurements from different satellites with overlapping time periods.
Sources of solar irradiance variability are spectral dependent, which is much more difficult to measure than TSI. Spectral variations are seen on the 27 day solar rotation cycle and also on the 11 year sunspot cycle.
IPCC AR5 climate model simulations are using the reconstruction from Wang, Lean, Sheeley (2005). Other recent estimates of long term solar variability: Kirova et al. 2011, Shapiro et al. 2011.
NRL’s general linear climate model: ENSO + volcanic aerosols + solar activity + anthropogenic effects explains 85% of the CRU temperature variance for the period 1979-2010.
Natural components account for <15% of warming since 1890. Claims that the sun has caused as much as 70% of recent warming presents fundamental puzzles. It requires that
- the sun’s brightness increases more than current understanding allows
- Earth’s climate be insensitive to well-measured increases in greenhouse gases at the same time that it is excessively sensitive to poorly known solar brightness change
How and why will temperature change in the next few decades? Future near-term climate change will vary because of both natural and anthropogenic influences. Her model predicts a warming of 0.4C by 2030.
Predicts solar cycle 24 will be less active than cycle 23
A pending maunder minimum? Well everyone is predicting a solar cycle decrease, with most other studies predicting more of a decrease than Wang, Lean, Sheeley 2005.
- Decadal trends in solar irradiance are not yet detectable from uncertainties caused by instrument instabilities in observations: historical irradiance reconstructions are very uncertain
- Natural influences, including solar irradiance variations, alter Earth’s surface temperature, atmosphere and ozone
- Natural influences and anthropogenic influences have different strengths in the stratosphere relative to the surface
- Surface temperatures will continue to increase Lower stratospheric temperature will remain at about current levels Total ozone will increase, exceeding 1980 levels as soon as 2025
- Improved CCM & GCM ability to reproduce responses to solar cycle: validation and improvements still needed
Climate model response to radiative forcing:
- Current understanding assumes that climate response to solar radiative forcing is thermodynamic
- Empirical evidence suggests it is dynamic, rather than (or as well) as thermodynamic
- Engages existing circulation patterns (Hadley, Ferrel and Walker cells) and atmosphere ocean interactions (ENSO)
- Involves both direct (surface heating) and indirect (stratospheric influence) components
Three different TSI measurement composites (since 1980) provide diffrences in absolute scale, temporal structure, solar minimum levels, long-term trends.
- Irradiance decrease from 1996 to 2008 solar minimum claimed to produce global cooling . . . but decrease in PMOD and ACRIM composites could be instrumental
- Irradiance increase from 1986 to 1996 solar minimum claimed to produce 20-30% of recent global warming . . . but increase in ACRIM composite could be instrumental
Solar cycle irradiance modulates:
- stratospheric vortex
- tropospheric circulation
- NAO (solar min) AO (solar max) (Kodera 2003)
An actual Maunder Minimum can take > 100 years – not 10 years – to eventuate. A new Maunder Minimum will NOT cause another Little Ice Age.
Svalgaard’s ppt file is less easy to interpret in stand alone form, with little text, but I reproduce his conclusions here:
- Solar activity is now back to where it was a century ago (Shouldn’t TSI also not be?) Note: Shapiro et al. (2o11) find major increase relative to 100 years ago (~5 W m-2)
- No Modern Grand Maximum (in sunspot numbers)
- Cosmic Ray Modulation discordant
- Solar influence on climate on shaky ground if we don’t even know solar input
Der Spiegel has an article on this topic, an interview with German electric utility executive Fritz Vahrenhold, entitled “I feel duped on climate change.”
Will reduced solar activity counteract global warming in the coming decades? That is what outgoing German electric utility executive Fritz Vahrenholt claims in a new book. In an interview with SPIEGEL, he argues that the official United Nations forecasts on the severity of climate change are overstated and supported by weak science.
There is significant uncertainty, not only in solar reconstructions, but in the interpretation of satellite measurements since 1980. There is a 6 W m-2 discrepancy in the baseline measurements across different satellite systems, plus significant differences in trends since 1980. There is 5 W m-2 discrepancy in the reconstructions in the first few decades of the 20th century. For reference, the 20th century CO2 forcing is 1.7 W m-2.
While this uncertainty seems generally acknowledged in the solar community and by Judith Lean (who has been the main solar person involved in the IPCC), I have to say I’m concerned that the CMIP climate model experiments for the IPCC uses only one solar reconstruction.
The IPCC has framed the climate change problem in the context of anthropogenic forcing, and national funding has followed suit. There has been far too little emphasis on understanding the sun and solar-climate interactions, I see a few signs that this situation is improving.
Re AR5, I haven’t checked to see who the solar authors are or what the ZOD has to say?
Moderation note: comments will be moderated for relevance.