The text of her talk and copies of the slides were provided as ATCM XXIX IP 76. [Readers, I believe this lecture was given in 2006, but the data is still true.]
The PowerPoint slides are available separately on the SCAR web site, at www.scar.org/communications/.
Dr Masson-Delmotte explained that ice cores provide unique climate archives containing information on past climate and environmental changes at local, regional and global scales. The isotopic composition of the water trapped as ice allows us to estimate the past temperature of the Antarctic region. The chemical composition of the ice also includes information on dust and aerosols transported by the atmosphere, which help us to understand the extent of droughts and volcanic activity on surrounding continents. Finally, air bubbles trapped in the ice enable us to determine the composition and abundance of greenhouse gases in the atmosphere through time. Comparing the data from the present with those from the past enables us to determine the impact of human activities on the composition of the atmosphere. Comparison with the past record, and knowledge of the way in which the Earth receives radiation over periods of thousands of years during its orbit around the sun, suggests that the Earth today is in a long “interglacial”, which should last a further 30,000 years before the descent into a new ice age. The data from air bubbles trapped in the ice show that the present levels of the greenhouse gases methane and CO2 are considerably higher than anything experienced in the atmosphere of the last 650,000 years. These increases are entirely due to human activities (intensive agriculture and massive use of fossil fuels). Temperature is also increasing. The rate of increase in temperature over the past 100 years has taken place 25 times faster than any natural changes over the past 650,000 years.
Link to page 7 of the pdf file (Annex H, page 497): http://www.ats.aq/documents/atcm_fr_images/ATCM29_fr004_e.pdf
No comments:
Post a Comment