Geoscience Reference
In-Depth Information
whereby only a very small number of well-publicized studies establish a paradigm that may not be
supported by most records.
General circulation models (with a well-developed stratospheric chemistry component) could be
used to assess the possible effects of solar irradiance changes (total and UV) on global and regional
climate and thereby guide a paleoclimate research strategy. Current models suggest that climate effects
are possible, even with relatively small changes in total irradiance (though most models have used larger
changes in TSI than current research suggests is likely). Importantly, they indicate that there may have
been distinct changes in atmospheric circulation, resulting in regional patterns of climate change, rather
than simply overall warming or cooling.
This field cries out for a more systematic and rigorous approach to determine whether solar
forcing has played an important role in past climate changes. A well-designed and statistically rigorous
strategy, using a network of well-dated high-resolution proxies, in association with general circulation
modeling studies, is needed.
Detecting the Solar Cycle via Temperature Proxies Back to the Maunder Minimum
Gerald R. North, Department of Atmospheric Sciences, Texas A&M University
This talk focuses on the very faint (a few hundredths of a degree centigrade) temperature
signature associated with the 11-year solar cycle. If solar TSI changes were the only cause of the
response, a simple climate model could be used to map the amplitude and phase lag of the response over
the planet. One can use regression/detection methods to estimate the strength of the signal simultaneously
with the volcanic, greenhouse, and aerosol signals. The signal strength is consistent with this kind of
forcing and response. Data from ice cores can also be used to detect the 11-year response through the 18 O
isotope record. Such a peak in the spectra is indeed present in several cores from Greenland and
Antarctica. Data from the core taken from Taylor Dome in Antarctica have a high enough signal-to-noise
ratio that one can reconstruct the time series in a narrow band about the 11-year peak by band-pass
filtering. The reconstruction clearly shows the Maunder Minimum at its correct time. The Dye-3 core
from southern Greenland shows some indications of the same, but the signal-to-noise ratio is less
favorable. This research represents an independent indicator, based on temperature response, of past solar
influences in forcing climate change at the decadal timescale.
Climate Response at Earth's Surface to Cyclic and Secular Solar Forcing
Ka-Kit Tung, University of Washington
I will review recent results on responses at the surface to the 11-year solar cycle and to the
longer-term secular trend in the longest global temperature dataset. Finally I will discuss some new
results on analyzing the 350-year Central England temperature record back to the Maunder Minimum, to
see if there is a larger solar signature.
Solar Effects Transmitted by Stratosphere-Troposphere Coupling
Joanna Haigh, Imperial College, London
Data from satellite-borne radiometers indicate that total solar irradiance is greater when the Sun is
more active, by about 0.1 percent at the maximum relative to the minimum of the 11-year cycle. Based
on simple energy balance arguments, and a standard estimate of climate sensitivity to radiative forcing,
this translates into a variation in the global mean surface temperature of around 0.1 K over the solar cycle.
Analysis of observational records concurs with this, but the distribution of the solar signal is decidedly
non-uniform. Within the troposphere the largest response occurs in midlatitudes with bands of warming
Search WWH ::

Custom Search