2011 Global Warming Seminar Series

We now know the root causes of the global warming and ocean-acidification that are underway on our planet. These are no longer an issue of science, for the science is clear enough. Indeed, that clarity now allows us to speculate with increasing confidence what the future holds...and the prospect is not pretty. But despite the convergence of theory and observation, despite the increasing impacts of a changing climate, and despite insults to nature like ocean acidification, we largely remain reluctant to act. This talk will not address that reluctance; that task is better left to political scientists, philosophers, economists and human...

Understanding the causes of climate change is one of the most important challenges facing science today. The Intergovernmental Panel on Climate Change attributes more than 90% of the observed warming during the last century to anthropogenic causes, especially the increase in atmospheric carbon dioxide from fossil fuels. However, during the last ten thousand years since the end of the last ice age, and prior to industrialisation, the climate has frequently changed on 100-year time scales by amounts comparable to the current warming. At present there is no established mechanism to explain these natural climate changes, but associations are...

I will begin with a brief primer on the physics of climate change, and how it is represented in climate models, and how the models are tested with observations. This will be followed by a discussion of how clouds and water vapor modulate the Earth's climate through their radiative effects, through the effects of the large latent heat of water on atmospheric energetics, and by rapidly transporting energy, mass, and momentum across thick layers of air.

A description of the role of the various components of the climate system (the atmosphere, ocean, land and ice) in climate variability and change highlights the heat capacity of the oceans and the dynamics of the atmosphere and the ocean. The ocean also plays a major role in the water cycle as seen through changes in salinity and fresh water (salt) transports by currents. Melting land ice contributes to sea level rise and so does ocean expansion. The overall flow of energy through the climate system and its uptake by the oceans in summer and discharge in winter will be discussed along with ocean and atmospheric heat (energy) transports....

The dramatic decline of the summer Arctic sea ice pack is probably the most visible, large scale change on Earth's surface in recent years. Most global climate models, however, have significantly underestimated this decline. We will discuss how models from statistical physics are being used to study key sea ice processes such as the formation and melting of seasonal ice. Such processes must be better understood to improve projections of the fate of the polar ice packs, and the response of polar ecosystems. We will also discuss evidence of climatic warming exhibited by the great land ice sheets of Greenland and Antarctica. Video from a...

The modern instrumental surface temperature record extends back in time over about one and a half centuries. Since 1850, the number of points at which temperature is observed has increased enormously although even today, there remain many places on Earth where temperature is not routinely observed and reported. Such data gaps do not pose a serious impediment for the reliable estimation of changes in global mean temperature, as has been demonstrated by both empirical and theoretical research. A greater potential concern is that temperature observations are often affected by non-climatic influences including changes in instrumentation,...