And what we've done now, and with colleagues from Germany, is to take cores off north west Africa, say about twenty metres down into the sediment, we sample them in the lab here and took the small amounts of sediment and examined them for these long chain compounds and we were extremely excited to see that as we went down this core, back through the last few hundred thousand years, we could see our signal on sea surface temperature oscillating about roughly in the same way that er has been found with other methods of getting at the past history of the climate.