Title: Solar Warming?
Source: World Climate Report
URL Source:
http://www.worldclimatereport.com/in...solar-warming/
Published: Mar 22, 2006





Just when you were starting to believe that variations in the amount of
energy coming from the sun weren't responsible for much of the observed
surface warming during the past 20 years, comes along a paper in Geophysical
Research Letters from two researchers at Duke University, Nicola Scafetta
and Bruce West, that concludes otherwise:

We estimate that the sun contributed as much as 45-50% of the 1900-2000
global warming, and 25-35% of the 1980-2000 global warming. These results,
while confirming that anthropogenic-added climate forcing might have
progressively played a dominant role in climate change during the last
century, also suggest that the solar impact on climate change during the
same period is significantly stronger than what some theoretical models have
predicted.

Scafetta and West arrive at their conclusions after applying a mathematical
scheme that allows the cycles in solar variations to explain the cycles in
temperature variations. They find this empirical method far superior to
theoretical (i.e. climate models) methods because empirical methods take
advantage of real behavior while theoretical methods are just
that-theories-which very likely do not capture all of the real-world
intricacies relating solar energy to climate processes.

The authors summarize:

The sun played a dominant role in climate change in the early past, as
several empirical studies would suggest, and is still playing a significant,
even if not a predominant role, during the last decades. The impact of solar
variation on climate seems significantly stronger than predicted by some
energy balance models.The significant discrepancy between empirical and
theoretical model estimates might arise because the secular TSI [total solar
irradiance] proxy reconstructions are disputed and/or because the empirical
evidence deriving from the deconstruction of the surface temperature is
deceptive for reasons unknown to us. Alternatively, the models might be
inadequate because of the difficulty of modeling climate in general and a
lack of knowledge of climate sensitivity to solar variations in particular.
In fact, theoretical models usually acknowledge as solar forcing only the
direct TSI forcing while empirical estimates would include all direct and
indirect climate effects induced by solar variation. These solar effects
might be embedded in several climate forcings because, for example, a TSI
increase might indirectly induce a change in the chemistry of the atmosphere
by increasing and modulating its greenhouse gas (H2O, CO2, CH4, etc.)
concentration because of the warmer ocean, reduce the earth albedo by
melting the glaciers and change the cloud cover patterns. In particular, the
models might be inadequate: (a) in their parameterizations of climate
feedbacks and atmosphere-ocean coupling; (b) in their neglect of indirect
response by the stratosphere and of possible additional climate effects
linked to solar magnetic field, UV radiation, solar flares and cosmic ray
intensity modulations; (c) there might be other possible natural
amplification mechanisms deriving from internal modes of climate variability
which are not included in the models. All the above mechanisms would be
automatically considered and indirectly included in the phenomenological
approach presented herein.

The bigger the observed solar impact, the smaller the observed human impact.
The smaller the human impact, the less sensitive the climate is to
greenhouse gas emissions. The less sensitive the climate is to greenhouse
gas emissions, the less the impact greenhouse changes (and greenhouse gas
emissions restrictions) will have in the future.

Reference:

Scafetta, N., and B. J. West, 2006. Phenomenological solar contribution to
the 1900-2000 global surface warming. Geophysical Research Letters, doi:
1029/2005GL025539.