Title: The Impact of Solar Variability on the Climate Derived from Long-Term Paleoclimatic Records
Author: J. Beer
Affil: EAWAG
Email: beer@eawag.ch
Abstract: Paleoclimate records from natural archives such as ice and sediment cores clearly show that the climate was never stable in the past. There is growing evidence that, among other factors, solar forcing is an important cause of climate change. Whereas the history of solar variability can be reconstructed over many millennia by means of cosmogenic nuclides (10Be, 14C etc.) the relationship between solar variability and solar forcing is not yet well understood. However, it is interesting to note that many abrupt changes in solar activity can be attributed to climate changes.
Title: Detecting the Solar Cycle in the Earth's Temperature Field
Author: Gerald R. North
Affil:
Authors: Qigang Wu
Abstract: There are four external forcings that are thought to perturb the planetary temperature field: Greenhouse Gases (G); Anthropogenic aerosols (A); Volcanic Dust Veils (V); and Solar Luminosity (S) changes. We have embarked on a program to detect the amplitude of the responses of the temperature field to these forcings. This talk will report the results of our studies to date: G and V are very signficant statistically, while A is problematic and S is marginally significant. The solar signal S is very interesting from a model-testing point of view since it is one of the few external forcings which is at the decadal scale and which could be used to test models at that time scale. We are currently investigating some ways to improve the performance of our detection procedure by including such effects as seasonality of the response fields and the inclusion of vertically distributed data. Preliminary results of these endeavors will be reported.
Title: Modelling studies of the response of the lower atmosphere to solar variability
Author: Joanna D. Haigh
Affil: Imperial College of Science, Technology and Medicine, London, UK
Email: j.haigh@ic.ac.uk
Authors: John Austin, Neal Butchart, Michael Palmer
Affils: UK Meterological Office
Abstract: General circulation models have been used to simulate the effects of varying solar spectral irradiance on the atmosphere. The results of several experiments will be discussed:
1. The response of the climate of the troposphere to variations in irradiance as experienced over the 11-year solar cycle is studied using two different GCMs with fixed sea surface temperatures. A robust mode of response is found in the zonal mean temperature and wind fields, especially at low latitudes and across the summer hemisphere, with polewards shifts of the sub-tropical jets and weakening of the winter Hadley cell. This pattern is compared to that found in response to other factors which affect the heat balance of the lower stratosphere (e.g. QBO, volcanic aerosol).
2. A model of the atmosphere up to 0.01hPa with coupled stratospheric chemistry is used to investigate the response of stratospheric ozone and temperature to solar variability on 27-day and 11-year timescales. The ozone response more closely resembles that seen in satellite observations than seen in previous (2D chemical transport) models.
3. A GCM with coupled slab ocean is used to investigate climate response to a reduction in solar irradiance of a magnitude estimated for the Maunder Minimum relative to the present. The ocean coupling enhances the response seen in the atmosphere-only simulations. Inclusion of ozone changes further enhances the signal but the overall magnitude is still not as large as detected in the observational temperature record.
Title: Effects of Particle Flux Variations on Clouds and Climate
Author: Brian A. Tinsley
Affil: University of Texas at Dallas
Email: Tinsley@UTDallas.edu
Abstract: The latitude distribution of ionosphere-earth current density in the global electric circuit responds to changes in the fluxes of precipitating energetic particles, including galactic cosmic rays. This current density polarizes clouds in the troposphere, beginning as they are forming, producing layers of space charge at cloud tops and cloud base. Mixing and evaporation processes result in charged nuclei that are subject to rapid electroscavenging.
For cold clouds (tops below freezing) electroscavenging leads to the production of ice by contact ice nucleation. For warm clouds, electroscavenging may reduce the concentration of small condensation nuclei, and enhance the concentration of 'giant' condensation nuclei, leading to larger average sized droplets. For both cold and warm clouds, and especially for marine stratocumulus, electroscavenging is likely to enhance the formation of precipitation (ice particles or drizzle droplets) and reduce the amount of cloud cover.
The above processes can be regarded as indirect effects of particle flux variations on clouds, in contrast to possible direct effects involving ion induced nucleation from the gas phase.