Attribution of twentieth century temperature change to natural and anthropogenic causes |
| |
Authors: | P A Stott S F B Tett G S Jones M R Allen W J Ingram J F B Mitchell |
| |
Institution: | (1) Hadley Centre for Climate Prediction and Research, The Met. Office, Bracknell, Berks, UK, RG12 2SY E-mail: pastott@meto.gov.uk, GB;(2) Rutherford Appleton Laboratory, Oxford, UK, GB |
| |
Abstract: | We analyse possible causes of twentieth century near-surface temperature change. We use an “optimal detection” methodology
to compare seasonal and annual data from the coupled atmosphere-ocean general circulation model HadCM2 with observations averaged
over a range of spatial and temporal scales. The results indicate that the increases in temperature observed in the latter
half of the century have been caused by warming from anthropogenic increases in greenhouse gases offset by cooling from tropospheric
sulfate aerosols rather than natural variability, either internal or externally forced. We also find that greenhouse gases
are likely to have contributed significantly to the warming in the first half of the century. In addition, natural effects
may have contributed to this warming. Assuming one particular reconstruction of total solar irradiance to be correct implies,
when we take the seasonal cycle into account, that solar effects have contributed significantly to the warming observed in
the early part of the century, regardless of any relative error in the amplitudes of the anthropogenic forcings prescribed
in the model. However, this is not the case with an alternative reconstruction of total solar irradiance, based more on the
amplitude than the length of the solar cycle. We also find evidence for volcanic influences on twentieth century near-surface
temperatures. The signature of the eruption of Mount Pinatubo is detected using annual-mean data. We also find evidence for
a volcanic influence on warming in the first half of the century associated with a reduction in mid-century volcanism.
Received: 24 January 2000 / Accepted: 20 April 2000 |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|