Five centuries of global records of climate change from geothermal data
Abstract
Energy at the Earth's surface propagates into the subsurface by conduction, thus ground surface temperature histories (GSTH) can be retrieved from temperature versus depth profiles measured in boreholes. Here we report on the analysis of 776 borehole temperature profiles from all continents except Antartica in order to examine the spatial patterns of GST variation over the last five centuries. The reconstruction is based on a 1D heat conduction model and was carried out using a singular value decomposition inversion algorithm. In order to preserve the same number of principal components at each site, the same eigenvalue cutoff was used in the analysis. Individual GST histories show high spatial variability. Results show that a 1 \deg K ground temperature increase has taken place during the last 500 years, but local colder or warmer short-term excursions interrupted this global trend. We observed that the warming occurs sooner in the southern hemisphere and that a general cooling, more intense in North America and Europe occurred around the end of the 19th century which is in agreement with the local meteorological record. The global bimodal latitudinal distribution of temperature (above and below 40 \deg N) seems to be less striking since the beginning of the last century during which the largest warming occurs. The latitude-weighted average northern high latitude GSTH shows a cold period from the mid-18th to the end of the 19th century that may be evidence of the "Little Ice Age" cold period (LIA). The LIA is not clearly observed elsewhere.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004AGUSMGC41A..05B
- Keywords:
-
- 1600 GLOBAL CHANGE;
- 1620 Climate dynamics (3309);
- 1645 Solid Earth;
- 3309 Climatology (1620);
- 3344 Paleoclimatology