Stupid Earth!
Something finally clicked in my head.
The local climate summary for October, 2005, has this to say [stupid HTML, make table-making a pain in the...hey hey!]:
Values given in this order: Normal, Oct. 2005, Difference
Temps:
Avg. Daily High (ADH): 68.0°, 67.8°, -0.2°
Avg. Daily Low (ADH): 49.6°, 53.1°, +3.5°
Daily Avg. Temp (DAT): 58.8°, 60.4°, +1.6°
The avg. daily high (ADH) was actually lower than normal. So, one might reasonably ask, how can one claim things have warmed up?
The ADH is not the important measure. The important measure is the average distribution, or at least the average range. Normally, this is from 49.6° to 68.0°, a range of 18.4°. This year, though, it was 53.1° to 67.8°, a range of 14.7°. So the average range was 3.7° (18.4 - 14.7) less than usual. Since the ADH was only 0.2° (68.0 - 67.8) less than normal, the extra 3.5° (3.7 - 0.2) had to come from the bottom, as indeed it did: avg. daily low (ADL) this year was 3.5° warmer than normal.
Global warming is not a simple matter of high temperatures getting higher. It's a matter of the atmospheric heat budget.
No, it didn't get quite as hot as normal this year, but it stayed much warmer overall, as we can tell from the 1.6° increase in daily average temperature (DAT) compared to the normal value.
Temperature is a proxy measure for the amount of heat in the atmosphere. The 3.5°-higher-than-normal ADL this year more than compensates for the 0.2°-lower-than-normal ADH, so we can say that there was more heat overall in the local atmosphere this year than there normally is. That is how global warming is going to manifest.
This might not matter all that much in temperate latitudes and elevations. (Then again, it might: should tropical regions warm up more than polar ones, there'd be a latitudinal temperature gradient, meaning that air masses would be more likely to have greater differences in temperature along their fronts, meaning that any resulting storms would probably be stronger.) But it definitely will matter in tropical and polar ones.
If the air in the tropical Atlantic doesn't cool down so much at night, there will be less heat lost from ocean to air, and therefore that much more heat available to drive hurricanes. There's a threshold ocean temperature for hurricane formation, but it's only a necessary condition, not a sufficient one: other conditions must obtain. Once a hurricane has formed, though, by far the single most important factor in determining its strength is ocean temperature. Thus, hurricanes may not become significantly more common, but they will probably be stronger.
Likewise, if the ADH in a glaciated region hovers at around, say, 40°, but the ADL rises from, say, 18° to 22°, you could very well see a DAT rise from 31° to 33°. And then you're in position for net ice loss.
We don't need blistering summers to suffer from global warming. Just enough extra heat to keep things from cooling down quite so much at night is all it takes.
The local climate summary for October, 2005, has this to say [stupid HTML, make table-making a pain in the...hey hey!]:
Values given in this order: Normal, Oct. 2005, Difference
Temps:
Avg. Daily High (ADH): 68.0°, 67.8°, -0.2°
Avg. Daily Low (ADH): 49.6°, 53.1°, +3.5°
Daily Avg. Temp (DAT): 58.8°, 60.4°, +1.6°
The avg. daily high (ADH) was actually lower than normal. So, one might reasonably ask, how can one claim things have warmed up?
The ADH is not the important measure. The important measure is the average distribution, or at least the average range. Normally, this is from 49.6° to 68.0°, a range of 18.4°. This year, though, it was 53.1° to 67.8°, a range of 14.7°. So the average range was 3.7° (18.4 - 14.7) less than usual. Since the ADH was only 0.2° (68.0 - 67.8) less than normal, the extra 3.5° (3.7 - 0.2) had to come from the bottom, as indeed it did: avg. daily low (ADL) this year was 3.5° warmer than normal.
Global warming is not a simple matter of high temperatures getting higher. It's a matter of the atmospheric heat budget.
No, it didn't get quite as hot as normal this year, but it stayed much warmer overall, as we can tell from the 1.6° increase in daily average temperature (DAT) compared to the normal value.
Temperature is a proxy measure for the amount of heat in the atmosphere. The 3.5°-higher-than-normal ADL this year more than compensates for the 0.2°-lower-than-normal ADH, so we can say that there was more heat overall in the local atmosphere this year than there normally is. That is how global warming is going to manifest.
This might not matter all that much in temperate latitudes and elevations. (Then again, it might: should tropical regions warm up more than polar ones, there'd be a latitudinal temperature gradient, meaning that air masses would be more likely to have greater differences in temperature along their fronts, meaning that any resulting storms would probably be stronger.) But it definitely will matter in tropical and polar ones.
If the air in the tropical Atlantic doesn't cool down so much at night, there will be less heat lost from ocean to air, and therefore that much more heat available to drive hurricanes. There's a threshold ocean temperature for hurricane formation, but it's only a necessary condition, not a sufficient one: other conditions must obtain. Once a hurricane has formed, though, by far the single most important factor in determining its strength is ocean temperature. Thus, hurricanes may not become significantly more common, but they will probably be stronger.
Likewise, if the ADH in a glaciated region hovers at around, say, 40°, but the ADL rises from, say, 18° to 22°, you could very well see a DAT rise from 31° to 33°. And then you're in position for net ice loss.
We don't need blistering summers to suffer from global warming. Just enough extra heat to keep things from cooling down quite so much at night is all it takes.
posted by Dr. Bubbles at 15:22
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