Climate Change

Although global temperature rise is widely discussed concerning the severity of climate change, a more societally relevant concern is how weather and climate will vary at the local and regional level. Temperature rises over very large spatial scales (e.g., a hemisphere or the globe) do not imply uniform changes of various climatic variables (hurricanes, droughts, storms, etc) but we should expect global inhomogenities in climate as greenhouse gases build up in the atmosphere. For example, changes in global mean precipitation (or evaporation) are not incredibly large in a warmer world; models tend to agree that there is a less than 2% increase per degree C global mean warming. However, changes in horizontal transport and increased precipitation gradients (drier areas getting drier, wetter areas getting wetter, droughts in areas, flooding in others, etc) are a big reason for concern. What’s more, people will inevitably be concerned about the likelihood of extremes, such as the possibility of more anomalous events like the European heatwave of 2003.

The first federal review of research on how global warming may affect extreme climate events in North America is available here. Regions of focus include North America, Hawaii, Caribbean, and U.S. Pacific Islands. A summary of findings below:

Read the rest of this entry »

Modern climate science tells us that increased emissions of greenhouse gases, most notably carbon dioxide, will change the climate that we are used to and have consequences for ecosystems and societies worldwide. A rise of just several degrees can have large and widespread impacts that dramatically alter civilization, but there are worries aside from a slow and steady rise. Climatic records show that large, widespread, and abrupt climate changes have occurred repeatedly in the past. Dr. Richard Alley of Penn State University has lectured on this topic and has used an analogy of the climate being like a drunken college student– when you don’t do much to it then it will just sit there, but if you move it around a little bit then it will stagger about and maybe fall. The last ten thousand years or so (the Holocene) has been an unusual time of relative calmness, with little variation in the climate. However, for most of the last 100,000 years, and even before, this has not been the case. One of the potential threats that comes from altering the chemistry of the atmosphere, and changing the land around to suit or needs, is the ability to flip a “climate switch” and force it between different states. Other possibilities include crossing critical thresholds, such as melting the arctic sea ice, that will have large socio-economic and/or ecological consequences. Such events have been labeled “tipping points” and many scientists (notably James Hansen of NASA, Alley, and others) have started to issue many warmings that the Earth may not respond to a new climate is a nice and steady fashion.

Read the rest of this entry »

In the latest issue of Science, Hoegh-Guldberg et al. 2007 (subscription required) reports on the effects on coral reefs due to the strong influences of both the increase in global temperatures, and the acidification of ocean because of high atmospheric CO2 levels, of which are now higher than any time in at least 800,000 years, and probably longer.

Read the rest of this entry »

The following images were presented by Dr. Lonnie Thompson at the latest AGU conference in California, in a powerpoint presentation. Just gives a bit of a persective on what is going on around the world. Ice is one of the first reactors to a climate change, and the pictures show that we are in a new climate. The images are from different parts of the world: the Himalays in Tibet, to the Andes in South America, Alaska, Glacier National Park, Italy, Africa, etc

Read the rest of this entry »