Nitrous oxide and methane variations covering the last 100,000 years: Insight into climatic and environmental processes
This year, another record-breaking hot and dry summer in large parts of Europe has once more caught the attention of the public and raised questions about climate change and global warming. The evidence is growing that human activities affect the climate system, primarily through the emission of gre...
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| Other Authors: | , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
| Published: |
2003
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| Online Access: | https://boris.unibe.ch/192466/1/flueckiger03phd.pdf https://boris.unibe.ch/192466/ |
| Summary: | This year, another record-breaking hot and dry summer in large parts of Europe has once more caught the attention of the public and raised questions about climate change and global warming. The evidence is growing that human activities affect the climate system, primarily through the emission of greenhouse gases and aerosols, resulting in significant warming observed over the last century [IPCC, 2001]. In the discussion of climate change, records of climate variations in the past play a crucial role for several reasons. First, paleodata are used to study mechanisms and feedbacks operating in the climate system. Second, attribution of climate change to anthropogenic causes relies on the central finding that the observed trends are unusual. Here, reconstructions of the past climate provide insight into the range of natural climate variability. Third, the simulation of climate variations in the past and the validation with data remain one of the harshest test for the climate models that are used to predict future climate. And fourth, quantifying the effect of anthropogenic emissions of greenhouse gases on the climate requires precise knowledge of the global biogeochemical cycles. The reconstruction of atmospheric greenhouse gas variations in the past offers a unique opportunity to study the key biogeochemical processes. Climate change leaves its traces in a variety of archives, among them marine and lake sediments, tree rings, stalagmites, corals, and others. But many indicators record climate indirectly and/or reflect local as well as large-scale changes. Greenhouse gases are well-mixed over the Earth, reflect large-scale or global changes, and thus are exceptional in this respect. The large ice sheets provide an archive of ancient air trapped in small air bubbles that can be measured directly. Deep ice core drillings in Greenland and Antarctica have provided an often undisturbed record of greenhouse gas concentrations in the past. While atmospheric carbon dioxide (CO2) and methane (CH4) have been reconstructed ... |
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