Lake Tahoe’s surface temperature is rising faster than the air temperature. I haven’t read the underlying paper to understand their postulated mechanism, but if the study is valid, it seems to me that an increase in insolation is a more plausible mechanism than AGW. I also think that the concern about the increase creating a dead zone is overhyped.
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Could also be a change in albedo or opacity of the lake. It’s supposedly is silting up due to globa^H^H^H^H^H lakeside construction.
At first glance this does perhaps seem to me to be evidence of global warming. Oceans are of great depth and have huge thermal inertia – lakes are shallower and have proportionately higher river inflows. Air being highly mobile, would presumably be more directly linked to ocean temperature. Hence I might expect lake temperature to be a more direct and responsive measure of changing insolation, and if that is the case then this data would strongly infer that there is actually significant global warming. 1 degree F increase in lake temperatures over the last 50 years – far more than air or ocean temperatures I would think which suggests that air heat transfer is not the means of lake heating.
Considering their different thermal mass proportions, that lakes are warming at a different rate than oceans seems highly revealing with regard to revealing the direction and extent of the current underlying forcing function for global temperature.
Rechecking, a global average temperature increase of around 1 degree F is suggested by various sources over the last 50 years (whether they can be trusted or not…). This correlates closely with the change in lake temperature over the same time. So it could be that the lakes are just being heated by higher air temperatures – surface heating and river inflow temperatures (which likely correlate closely with average air temperature).
Could be as these man-made lakes like Tahoe fill with the sediment the river originally transported, they are losing depth and becoming warmer. Shallower lakes heat more quickly.
Tahoe is a natural lake.
The turnover in a lake may be affected by winds. Less wind, or wind from a different direction, and maybe there could be less mixing of the surface water with deep water.
I was thinking Lake Mead for some reason.
Tahoe has long been known for it’s intense clarity. Being able to see from the surface a dinner plate resting under 50′ of water. This is no longer true, due to exactly what Karl noted.
It’s also the coldest lake I’ve ever water skied on.
The ocean temps are also rising faster than the global air temperatures. Most of the warming of the global climate is being absorbed by the heat sink provided by water.
This is freshman physics, no mystery at all. Water has a very high specific heat, much higher than most rocks. So the oceans are absorbing more heat than the land, or the air.
I’ve been watching Lake Tahoe since I was a child – used to live in Tahoe City in the 1960’s. The waters have been polluted badly from their formerly pristine condition, mostly by construction runoff. It’s a serious problem.
And yes, it is very cold in that lake.
The ocean temps are also rising faster than the global air temperatures.
Even considering the much greater thermal inertia of the oceans? Surface temperature verse at depth?
If atmospheric CO2 is dominantly causing global warming then I would expect increasing air temperature to lead lake and ocean temperature increases.