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Coupled chemistry-climate models are being increasingly used to tackle the problem of understanding the mechanisms for driving changes in past, present and future atmospheric composition. Given the computational overheads of running these types of models the chemical mechanisms which are used are often chosen for their speed of simulation.
Reduced Arctic sea ice continues to be a palpable signal of global change. Record lows in September sea ice extent from 2007-2013 have fueled speculation that trans-Arctic shipping routes may become physically viable in the 21st century. These physical changes combined with increased resource demand in East Asia have recast the Arctic as an international trade space facilitating export of resources and offering potential alternative pathways for global maritime trade.
In this talk I will show that large-scale afforestation in the northern mid latitudes warms the Northern Hemisphere and alters global circulation patterns in climate model experiments. An expansion of dark forests increases the absorption of solar energy and increases surface temperature, particularly in regions where the land surface is unable to compensate with latent heat flux due to water limitation.
Models disagree about the average state of the tropical Pacific when subjected to enhanced greenhouse gas forcing and this uncertainty emphasizes the importance of reconstructing past variability in tropical Pacific climate, through episodes of known radiative forcing. Measurements of the modern and ice age tropical Pacific allow us to reconstruct the zonal gradient in nutrients over the past 4 million years—a gradient principally responding to upper ocean dynamics.
Rapid Arctic warming and sea ice reduction in the Arctic Ocean are widely attributed to anthropogenic climate change. The Arctic warming exceeds the global average warming due to feedbacks that include sea ice reduction and other dynamical and radiative feedbacks. We show that the most prominent annual mean surface and tropospheric warming in the Arctic since 1979 has occurred in northeastern Canada and Greenland.
Hydrologic applications of GPS site-position observations in the Western U.S.