ABSTRACT
Understanding anthropogenic climate change is essential for anyone working in the life sciences. Firstly because climate change has already started to impact the Earth biosphere and human health and these changes need to be documented and acknowledged. Secondly, many of the solutions to climate change, both mitigation and adaptation, will be through the life sciences, everything from massive reforestation and sustainable agriculture to preventing the spread of disease and protecting individual human health. Anthropogenic climate change is, therefore, one of the defining challenges of the 21st century, along with poverty alleviation, environmental degradation and global security. Climate change is no longer just a scientific concern but encompasses economics, sociology, geopolitics, national and local politics, law and health to name a few. Hence, to understand climate change fully then not only does one have to review the science but also the politics and geopolitics, which have created the issue and can provide the solutions. Climate change ultimately makes us examine the whole basis of modern society and ultimately asks questions about humanity's relationship with the rest of the planet.
ABSTRACT
The Palaeocene-Eocene thermal maximum (PETM), a rapid global warming event and carbon-cycle perturbation of the early Palaeogene, provides a unique test of climate and carbon-cycle models as well as our understanding of sedimentary methane hydrate stability, albeit under conditions very different from the modern. The principal expression of the PETM in the geological record is a large and rapid negative excursion in the carbon isotopic composition of carbonates and organic matter from both marine and terrestrial environments. Palaeotemperature proxy data from across the PETM indicate a coincident increase in global surface temperatures of approximately 5-6 degrees C. Reliable estimates of atmospheric CO(2) changes and global warming through past transient climate events can provide an important test of the climate sensitivities reproduced by state-of-the-art atmosphere-ocean general circulation models. Here, we synthesize the available carbon-cycle model estimates of the magnitude of the carbon input to the ocean-atmosphere-biosphere system, and the consequent atmospheric pCO(2) perturbation, through the PETM. We also review the theoretical mass balance arguments and available sedimentary evidence for the role of massive methane hydrate dissociation in this event. The plausible range of carbon mass input, approximately 4000-7000 PgC, strongly suggests a major alternative source of carbon in addition to any contribution from methane hydrates. We find that the potential range of PETM atmospheric pCO(2) increase, combined with proxy estimates of the PETM temperature anomaly, does not necessarily imply climate sensitivities beyond the range of state-of-the-art climate models.
ABSTRACT
Quantifying the moisture history of the Amazon Basin is essential for understanding the cause of rain forest diversity and its potential as a methane source. We reconstructed the Amazon River outflow history for the past 14,000 years to provide a moisture budget for the river drainage basin. The oxygen isotopic composition of planktonic foraminifera recovered from a marine sediment core in a region of Amazon River discharge shows that the Amazon Basin was extremely dry during the Younger Dryas, with the discharge reduced by at least 40% as compared with that of today. After the Younger Dryas, a meltwater-driven discharge event was followed by a steady increase in the Amazon Basin effective moisture throughout the Holocene.
