Borehole Data Suggests Global Warming is Global

Environmental News Service ^ | 04/16/2002

[cogitator]

It's important because subsurface heating is dominated by the heat production inside the earth once you get more than a few feet from the surface. If the data is deep at all, it indicates global warming from within having nothing to do with the sun and expecially nothing to do with our industrial activities.

The subsurface heat profile is taken into account. I would guess that these are mostly water wells or geophysical exploration (i.e. core profile), so they aren't that deep.

It seems to me that in this thread (which dates back to last April) that I posted links to the best explanations I could find of the method on-line. I'll check and refer you to the numbers in a subsequent reply.

[cogitator]

Read post 15 in this thread.

[RightWhale]

It gets complicated right away when material conditions change at the surface, insulation, and in the rock, thermal conductivity. You are reduced to using machine solutions to the heat equation, and then to say that climate change seeps into the rock at 3 feet per year is probably an upper limit if there is any vegetative cover since summer/winter gets only 1 foot or less into the soil around here. Some places there is permafrost starting 20 feet down and going deeper and you have to think it got cold for a long time to freeze it that deep and deeper, and then think it has been a long time of climate evolution to thaw down only 20 feet so far. A real long time. Whatever effect we are having on all this is seems like would be undetectable.

[cogitator]

You bring up legitimate questions with regard to the
data; however, I expect that these are questions that
the scientists performing the analyses have had to answer,
as well. Perhaps holes that are drilled through
permafrost can't be used; not all of the Arctic is
covered with permafrost. To make an analogy with ice
cores, at the bottom of a glacier core the record gets
pretty distorted; it seems logical that the top of
a borehole log is pretty flaky, but that it smooths out
further down.

[RightWhale]

these are questions that the scientists performing the analyses have had to answer

There is no doubt about it. They have probably developed something like a tree-ring history with at least a time scale and a temperature function so they can estimate what the temperature in the atmosphere was, say, 5000 years ago.

[cogitator]

http://www.enn.com/enn-news-archive/2000/02/02172000/borehole_10118.asp

The link above has a temperature profile derived from borehole temperatures. The plot goes back 500 years; the article says they can go back about 1,000 years.

The article also addresses some of the other questions you raised. The data does complicate the question of natural vs. anthropogenic warming, because the borehole data shows a 500-year warming trend that accelerated in the 20th century. But if the world was in a Little Ice Age period during that time, with surface ups and downs that are seen in the tree-ring and sediment core record, it makes sense that there has been warming since 1500 when the surface variability is smooothed out.