Aerosol and cloud effects on solar brightening and the recent rapid warming
David Schnare
10.1029/2008GL034228, 2008
Aerosol and cloud effects on solar brightening and the recent rapid
warming
Christian Ruckstuhl, et al:
Abstract
The rapid temperature increase of 1°C over mainland Europe since 1980
is considerably larger than the temperature rise expected from
anthropogenic greenhouse gas increases. Here we present aerosol
optical depth measurements from six specific locations and surface
irradiance measurements from a large number of radiation sites in
Northern Germany and Switzerland. The measurements show a decline in
aerosol concentration of up to 60%, which have led to a statistically
significant increase of solar irradiance under cloud-free skies since
the 1980s. The measurements confirm solar brightening and show that
the direct aerosol effect had an approximately five times larger
impact on climate forcing than the indirect aerosol and other cloud
effects. The overall aerosol and cloud induced surface climate forcing
is ~+1 W m-2 dec-1 and has most probably strongly contributed to the
recent rapid warming in Europe.
09 July 2008
From New Scientist Print Edition.
GOODBYE air pollution and smoky chimneys, hello brighter days. That's
been the trend in Europe for the past three decades - but
unfortunately cleaning up the skies has allowed more of the sun's rays
to pierce the atmosphere, contributing to at least half the warming
that has occurred.
Since 1980, average air temperatures in Europe have risen 1 °C: much
more than expected from greenhouse-gas warming alone. Christian
Ruckstuhl of the Institute for Atmospheric and Climate Science in
Switzerland and colleagues took aerosol concentrations from six
locations in northern Europe, measured between 1986 and 2005, and
compared them with solar-radiation measurements over the same period.
Aerosol concentrations dropped by up to 60 per cent over the 29-year
period, while solar radiation rose by around 1 watt per square metre
(Geophysical Research Letters, DOI: 10.1029/2008GL034228). "The
decrease in aerosols probably accounts for at least half of the
warming over Europe in the last 30 years," says Rolf Philipona, a co-
author of the study at MeteoSwiss, Switzerland's national weather
service.
The latest climate models are built on the assumption that aerosols
have their biggest influence by seeding natural clouds, which reflect
sunlight. However, the team found that radiation dropped only slightly
on cloudy days, suggesting that the main impact of aerosols is to
block sunlight directly.
Ken Caldeira
260 Panama Street
Stanford, CA 94305 USA
+1 650 704 7212; fax: +1 650 462 5968
kcal...@stanford.edu
http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab/
Stephen Salter
I thought that you might like to see an artist's impression of a spray
vessel with underwater turbines.
It is by John MacNeill jwmac...@mindspring.com 617-484-0740
who has granted free use for academic and teaching uses. It will be on
the front cover of the Phil. Trans. Roy. Soc. special issue on
geo-engineering which comes out in October.
I found it hard to believe the 10 million energy ratio between the extra
solar energy reflection and wind energy used by the boats. It is based
on my understanding of Twomey 1977 paper as interpreted for engineering
consumption by Schwartz and Slingo 1996. It has been checked by several
others and is the sort of ratio you need to modify, or as we prefer to
say stabilize, climate. If anyone can produce alternative ratios, based
on other input assumptions of initial CCN concentration, boundary layer
depth and drop lifetime, please get in touch.
Stephen
Emeritus Professor of Engineering Design
School of Engineering and Electronics
University of Edinburgh
Mayfield Road
Edinburgh EH9 3JL
Scotland
tel +44 131 650 5704
fax +44 131 650 5702
Mobile 07795 203 195
S.Sa...@ed.ac.uk
http://www.see.ed.ac.uk/~shs
--
The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.
Alan Robock
It is a nice drawing of the vessel, but you have the science wrong. You are
pumping spray into a clear atmosphere, not into clouds. And for some reason
there is very strong wind shear, with the spray being sheared off a little
distance above the ship. I thought the idea was to pump spray into maritime
stratocumulus. You do have a few trade cumulus in the background, but running
your ship in the atmosphere drawn here would not produce much climate change.
Alan
Alan Robock, Professor II
Director, Meteorology Undergraduate Program
Associate Director, Center for Environmental Prediction
Department of Environmental Sciences Phone: +1-732-932-9800 x6222
Rutgers University Fax: +1-732-932-8644
14 College Farm Road E-mail: rob...@envsci.rutgers.edu
New Brunswick, NJ 08901-8551 USA http://envsci.rutgers.edu/~robock