[DiscoverDave]

Does anyone know of other living indicators of global warming?  Melting icecaps seem to dominate the news.

It seems the US government uses lilac flowering dates to help understand global warming because lilacs have historically been a good predictor by blooming soon after the last spring frost and, on the average, they have been blooming earlier in more recent times. 

http://fhm.fs.fed.us/posters/posters08/supporting_docs/climate_change/global_change_impacts.pdf

http://www.ncdc.noaa.gov/paleo/phenology.html

Phenology is the study of the times of recurring natural phenomena, such as flowering or leafing out in plants, especially in relation to climate. Because many such phenomena are very sensitive to small variations in climate, their phenology is useful in the study of climate change.

http://education.arm.gov/outreach/publications/sgp/jan03.pdf

http://www.springerlink.com/content/t53500862l326806/

http://www3.interscience.wiley.com/journal/72509480/abstract

http://davesgarden.com/community/blogs/t/Meredith79/8341/
(Read the entry for Friday, September 19, 2008.)

Farmers and gardeners in the previous centuries used lilacs to forecast the dates of the last spring frost based on the flowering dates of the lilac plants.  This is especially critical for farmers in northern climates with short growing seasons, such as New England.  Planting crops too early ran the risk of a late frost destroying the seedlings.  Planting too late ran the risk of having shortened the growing season.  So, some farmers planted lilacs near their farmhouses and kept an eye on them as people today would monitor the Weather Channel.  So, as beautiful as lilacs are all by themselves, people also appreciated them for other reasons.   

Centuries later, the use of lilacs has also come in handy for “prospectors” (the kind with metal detectors looking for old dwelling sites and the antiques that may exist there).  As the smart ones romp through the woods or across the countryside, they know that, if they find lilacs, they should look around for a cellar hole, because they may have found a very old farmhouse site. 

[frethack]

As far as indicators from currently living specimens, using delta-¹⁸O and the Mg/Ca ratio in yearly calcite growth bands in corals is another method.  These same ratios in foraminifera from ocean sediment cores are also widely used, though it is exceedingly rare to find sediments so highly resolved that temperature changes on yearly time scales can be detected.  Benthic anoxic conditions are needed to prevent bottom feeders from churning up the sediments (the Cariaco Basin is the only one that I can think of off hand).  Also, typically the first few cm of sediment are blown off when the core is taken, and for low sedimentation rates (only a few centimeters per thousand years) this could equate to centuries of data lost before you even start.  Tree ring growth chronologies are also an essential tool.  A friend of mine is also using a technique that uses the inner ear bones (I think its the ear bones anyway) of fish to be able to determine short term changes in ocean temperature through delta-¹⁸O and Mg/Ca ratios.   

[JimBob]

(the Cariaco Basin is the only one that I can think of off hand). 

The Black Sea is anoxic - out-fall from the Danube would be preserved in the deeper parts of the basin.

[SkepticSam]

DiscoverDave
"It seems the US government uses lilac flowering dates to help understand global warming because lilacs have historically been a good predictor by blooming soon after the last spring frost and, on the average, they have been blooming earlier in more recent times. "


but aren't the dates of the first blooms only a matter of a few days to a few weeks difference from year to year? And don't they fluctuate from earlier to later year to year?
The monitoring of first blooms has been noted long before AGW became big, in fact, the earlier blooming dates are one reason why meteorologists use different dates for the start of meteorological seasons to those more commonly used to indicate astronomical dates.

phenology should not be seen as concrete proof of the effects of AGW. The changing urban environment and urban heat island effect can (I believe) change the flowering times. Changes in development of rural areas will also change flowering times.

[SkepticSam]

Frethack.

What you say is interesting, and I have very basic knowledge in the field. But short term changes in SST doesn't have to be caused by AGW does it?
Can it be due to cyclical patterns/events, la nina, el niño the IOD and other oceanic events that influence the SST?

[frethack]

You are correct.  The proxies listed are only to detect temperature fluctuations.  It is up to the scientist to interpret what the data means.