Lew Incze: A Review of Temperature Change Data in the North Atlantic

Lew Incze starts us out with an art history lesson, and a lesson about ice skating. It appears that in the period before 1550 there are very few landscape scenes of cold weather; 1550-1580 was a "little ice age" -- glaciers moved out of valleys in Norway and covered farms -- and you can see more landscape scenes showing people skating (an awkward hobby that was made far more viable with the invention of the double-edged steel blade, which let people dispense with clumsy poles and made the sport more popular). He moves us on with some graphs showing historical variations of temperature in the range of 1 degree C and their corresponding fluctuations in the economic price of commodities.

Current predictions of temperature increases are not limited to one degree C. We have to go very far back in the geologic time scale.

In the Ordovician age, CO2 was much higher than today with equivalent temperatures. But the composition of the planet -- where the land masses and the oceans were spread on the globe -- was very different. The conclusion: it's complicated. You can't make a straight line model.

What impacts temperature? Many things: The eccentricity of the earth's elliptical orbit. Variations in solar output. Hemispheric differences in the ratio of land/ocean. Distribution of land/ocean (continental drift). Emissions and uptakes of greenhouse gases. (two more -- missed the slide -- go back to add these later).

Some of these are well-known (e.g. solar output) and/or act over long periods of time (e.g. continental drift). Few are within the range of human activity.

We don't have highly resolved models of global ocean temperatures -- scale of the system is too big (even though we have very highly resolved models of smaller areas, like the Gulf of Maine). It's hard to link our highly resolved models of smaller systems to the global climate change modeling systems that exist.

Boothbay Harbor, Maine: a well developed record of water temperatures: 1924-present day. You see fluctuations in temperatures, but generally a 2 degree temperature increase from the 1920s until the present. There's a big spike in the graph, though. In the 1950s there was a 5 degree temperature increase; this dropped off in the 60s. The whole northeast was dominated by a warm, moist climate pattern with warmer-than-average winters (which means less mixing in the water, a change in moisture and nutrient mixing, and a far more stratified ocean from top to bottom -- all of which impact plankton development and distribution). These "bobbles" or shorter-term variations in temperature make it hard to discuss slow and permanent increases: comparing present temperature to the 1950s data would show a water temperature decrease.

Temperature is not the only thing that is important in a marine ecosystem. There's also stratification and vertical mixing, the length of the stratified season, and the salinity and nutrients of the source waters. The impacts of climate change: temperature of water will affect the north/south range of domains and species. Increased uncertainty and perhaps lower production during faunal transitions. Lots of uncertainty from a food web perspective, stemming from changes in plankton and other primary food sources.

What are we pretty sure about?

1) Precipitation is going to go up.
2) The frequency of "severe events" (e.g. rainfall of more than 2 inches in 48 hours) will increase.
3) Streamflows will go down (less precipitation stored as snow).
4) Increasing temperature will mean less mixing in the ocean waters in the Gulf of Maine. Milder winters really impact the ocean state for the spring and summer: less mixing will impact density and temperature of zones.

Look at the report at www.climatechoices.org, and the report by the German Advisory Council on Climate Change -- both very good, readable summaries.

Lew's slides are presented below, and are available online.



Q: What about the Gulf Stream -- what's the expected impact on the Gulf Stream?
A: the global models don't do a very good job with the Gulf Stream, especially where it touches the North Atlantic and the Gulf of Maine.

Q: What do you mean by a higher level of uncertainty?
A: As you shift the geography of communities, you don't really know what to look for. And these new higher temperatures depart from the data we have, so it's hard to know how future data will be connected to the data we've already studied.
A: Andy Pershing: the data we've seen emphasizes the value of a long time series of data. There are starting to be more systems and continuing monitoring systems -- a lot of time those are focused tightly on physics and on new whiz-bang technologies. But there's a lot of value in the old monitoring systems that have been going since the 1930s, just to keep an unbroken series of data collection.
A: Lew Incze -- the Gulf of Maine is on the forefront of combining many types of data. Although we don't have a climate change scientist here in the crowd.

As with all the talks, please feel free to chime in with comments, questions, helpful links to resources elsewhere, and clarifications.