Category Archives: ecology/impacts

Isotopes and Maple Syrup

I thought that this article was interesting, discussing this recent paper in the Journal of Agricultural and Food chemistry. The analysis revealed that the relative amount of carbon-13 in maple syrup have gone down since the 1970s, which they attribute to changing isotopic signatures from fossil fuel burning in the atmosphere. Discussion and implications for the food industry in the article.


Feedbacks, Sensitivity, and Practical application

The global, annual-mean surface temperature is the most widely used measure of climate change. In particular, scientists are very interested in how the globally averaged temperature will respond as a function of changed amounts of greenhouse gases in the atmosphere, changed amount of solar intensity, etc. The term “climate sensitivity” refers to how much temperature change the planet experiences from a given “forcing.” A forcing is an imposed change of the planet’s energy balance with space.

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On the Arctic sea ice

Sea ice extent in the Northern Hemisphere has exhibited large and anomalous declining trends over the last several decades. In particular, there has been over a 20% decline since 1979. Linear trends in arctic sea-ice extent since 1979 are negative in every month.Recently, there has been particular interest recently over a record-breaking year in 2007 which flew by the second-lowest year in 2005. There also has been a foot-race this year, which has kept me particularly interested over the last few weeks. For a while, it seemed that 2008 would clearly not surpass 2007, but due to the drop over the last few weeks, that may not be the case (although it probably will be). Sea ice extent as of September 7, 2008 is 4,739,844 km2, while 2007 minima reached 4,267,656 km2 on September 16th last year.

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U.S. Climate report- Weather and Climate Extremes in a Changing Climate

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:

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Tipping Points in the Earth’s Climate System

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.

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Corals in Peril

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.

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A glacier perspective

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

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