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Andrew Howes

Dissertation BSc

4190405

Abstract
Projections of precipitation remain problematic for climate models and so far, regional
projections of Amazonian precipitation are primarily based on climate models from
phase 3 of the Coupled Model Intercomparison Project (CMIP3). Using contemporary
climate models from phase 5 of the Coupled Model Intercomparison Project (CMIP5)
this research analysed future Amazonian precipitation in the context of: future regional
changes, projected changes in DSL, the impact of different greenhouse gas
concentrations on projected rainfall and the probability that future precipitation will return
to levels of the 2005 drought. Changes in precipitation were assessed using 12 climate
models from the CMIP5 for the future (2081-2100), relative to the present (1986-2005).
Results show that eastern Amazonia is likely to undergo significant reductions in
precipitation and projections of future southern Amazonian precipitation remain complex
and uncertain. Future precipitation in western Amazonia is generally predicted to remain
stable and increase under high-resolution ensemble simulations whilst northern
Amazonia’s future precipitation is largely expected to remain stable. Modelled
predictions of precipitation over Amazonia were generally predicted to fall over the next
century under RCP2.6 and RCP8.5 concentrations. However, precipitation in most
regions experienced an increase in intensity under the RCP4.5 scenario, which may be
caused by regional feedback mechanisms such as carbon dioxide fertilisation. This
study supports a shift in focus to a more intense regional based analysis of future
Amazonian precipitation along with enhanced analysis of the processes that influence
future precipitation. Furthermore, based upon simple robustness assessments through
12-model and high-resolution ensemble simulations, this research proposes assigning
metrics to individual models based on their ability to replicate past climate. With this
information, policymakers and climate researchers will benefit from a greater
understanding of future regional Amazonian precipitation and therefore be in an optimal
position to prevent future climate change.

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