Global Warming Seminar Series 2011 Abstracts

The Instrumental Temperature Record and what it tells us about Climate Change

Francis Zwiers
Director of the Pacific Climate Impacts Consortium, University of Victoria, B.C.

Date: Wednesday, February 23rd
Time: 12.30pm
Room: The IRMACS Theatre

Abstract

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, instrument exposure, and instrument location. A great deal of work has been done to remove or avoid those influences wherever possible. Urban heat islands affect some temperature measurements taken over land, but do not substantial affect trends in the global mean record. Estimates of global mean temperature from surface temperature compilations produced by several different research groups are similar, demonstrating robustness to the specific choices that are made in their development. The resulting global record has been studied extensively, and is considered to be reliable.

The record shows an overall warming combined with low- and high-frequency variability. That there is warming is indisputable and is supported by additional lines of evidence (such as cryosphere changes, ocean heat content increases, and sea level rise). Much variability results from internal processes in the climate system and natural external forcing, such as volcanic activity and solar output changes. However, these factors alone do not explain the observed temperature changes well; radiative forcing caused by increases in greenhouse gas concentrations and changes in aerosol loadings provides a more plausible explanation. Statistical comparisons between observed temperature changes and those simulated by climate models that take various external forcing agents into account, as well as analyses of other possible causes, led to the IPCC 2007 conclusion that "most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations".

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Climate Change and the Melting Polar Ice Caps

Kenneth M. Golden
Professor of Mathematics and Adjunct Professor of Bioengineering, University of Utah

Date:Wednesday, March 2nd
Time: 12.30pm
Room: The IRMACS Theatre

Abstract

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 recent Antarctic expedition where we measured sea ice properties will be shown.

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The Role of the Oceans in Climate

Kevin Trenberth
Senior Scientist and Head of the Climate Analysis Section, National Center for Atmospheric Research, Boulder, Colorado

Date: Wednesday, March 9th
Time: 12.30pm
Room: The IRMACS Theatre

Abstract

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 role of the ocean in climate change and issues related to understanding the heat budget from 2003 to 2008, when there was a stasis in warming at the surface, will be discussed. Uncertainties in observations limit the ability to fully understand the changing climate and where heat goes within the ocean before re-emerging to further change the climate.

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The Role of Clouds and Water Vapor in Climate Change

David Randall
Professor, Department of Atmospheric Sciences, Colorado State University, Fort Collins, Colorado

Date: Tuesday, March 15th
Time: 12.30pm
Room: The IRMACS Theatre

Abstract

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.

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The Cloud Experiment at CERN

Jasper Kirkby
Head of the CLOUD Experiment, CERN, Geneva

Date: Wednesday, March 23rd
Time: 12.30pm
Room: The IRMACS Theatre

Abstract

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 frequently found with solar variability, which is recorded in archives that measure past variations of cosmic ray intensity. This raises the intriguing question of whether cosmic rays may directly affect the climate. This talk presents an overview of the palaeoclimatic evidence for solar/cosmic ray forcing of the climate, and the initial results from the CLOUD experiment at CERN which is investigating and quantifying the physical mechanisms that may link cosmic rays with aerosols, clouds and climate.


Responding to the Climate Change Challenge

Thomas Pedersen
Professor and Director of the Pacific Institute for Climate Solutions, University of Victoria

Date: Wednesday, March 30th
Time: 12.30pm
Room: The IRMACS Theatre

Abstract

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 psychologists. Rather, we will explore steps that could (and should) be taken now to slow Canadian CO2 emissions, in particular making smarter use of our electrical-generation capacity. But in attempting to curb carbon emissions, missteps can be taken too--unwelcome effects can result where policy directives are developed in the absence of appropriate scientific underpinning and interdisciplinary input. The ethanol debacle in the United States provides a good example and will be discussed.

Although climate science has matured to the point where we are now refining rather than originating, its importance in informing climate mitigation and adaptation policies has never been stronger. But that in itself is not enough; as the ethanol and electricity-generation examples will show, climate science is only one piece of a much bigger jigsaw. If we are to make compelling gains in future policy development, science must be married with social science, law, and engineering. Interdisciplinarity needs to become a required practice rather than a buzzword. The talk will conclude with an overview of initiatives that PICS is taking toward that end that will ultimately--we hope--yield solutions.