You are correct, the time scale is important. However, the fact is the troposphere and land-ocean temperatures have not show an increase relative to April 1998. If global warming was taking place, they certainly would have increased in 8 years. The monthly data show no trend and the annual don’t neither relative to 1998.
This concept that el nino generated it own energy, plus given it was localized, doesn’t seem to make any sense to discount 1998.
You continue to use 1998 as a base line and you continue to look at very short periods to identify trending. That is the sort of thing that prompted the popular press (not serious scientists) to project a new imminent ice age in the early 1970s.
You need to look at trends extending over many years.
How many years? Maybe Earth’s last tropical period?
This is where the concept of a “data spike” is important: i.e., an isolated outlying value that doesn’t affect the larger trend. Yes, there was a significant temperature spike in 1998, but there was an overall rising trend from 1999 to 2006—temperatures did increase.
The fact that the 1998 spike was higher than the upper end of the gradual rise (so far, at least) doesn’t necessarily mean that the rising trend is insignificant.
Whoa. “Generated its own energy”? I don’t think anybody’s claiming that. Sentient Meat’s point seems to be that El Nino gets its energy from elsewhere in the ocean, not that it somehow spontaneously produces it.
Also, why should the “localized” nature of El Nino mean that it couldn’t have a global effect on climate? Volcanoes and human industrial emissions are relatively localized too, but they appear to have global effects on climate.
No, not if what you’re interested in is the hypothesis, of anthropogenic global warming due to human-produced greenhouse-gas emissions. For that, you need to compare data from the era of industrialization (when humans started significantly changing atmospheric concentrations of greenhouse gases) with data from earlier periods that had a similar climate.
Nah. Back to 1769 would be fine.
Frankly, I do not know how far back we “need” to go. I do know that, depending on the technology used, there are only so many years we can go back. Ice cores can take us back thousands of years; some satellite technology goes back fewer than 20 and some is still being developed.
However, as more than one poster has already indicated, every graph (including the ones to which you have linked) indicates that 1998 was an anomalous spike. Beginning any investigation from that year would skew the results.
If El Nino was deriving its energy from other places on Earth, wouldn’t the Earth’s total global energy / temperature still stay the same? Thus, the self generated concept if you want to discount 1998.
Plus the 1998 global land-ocean temperature didn’t show a corresponding increase in temperature … it didn’t, which you expected if El Nino was drawing its energy / temperature from other sources, net “zero”.
Total energy over the entire amount of the earth’s mass, maybe. Global temperature over its surface, no, not necessarily. After all, the earth isn’t completely or uniformly permeable to thermal energy everywhere.
(And a damn good thing, too, right? Considering that the vast majority of the earth’s mass is in its mantle and core, which are pretty fricking hot! :eek: If all parts of the earth had to stay in thermal equilibrium all the time, things would get mighty uncomfortable around here.)
You’re right. But I don’t see any indication of a lack of increase either. Tell you what, do a least-squares fit to a linear function and give us a confidence interval for the slope. If the best-fit slope and confidence are smaller than the claimed value for global warming rate, you might have something there.
Well let’s look at this graph combining the land-ocean / lower troposphere temperature variances for the years 1998 through 2006. Sorry that it is a little cluttered. The references and data links are provided in the individual previous graphs for each.
If the troposphere temperature warmed because of El Nino, wouldn’t the land-ocean have shown some decrease or at least have been lower based on an energy balance? They were both “high?”
http://img327.imageshack.us/img327/7861/ux42iv.gif
Below …
R^2 = 0.0028 … random, no trend …
X Coefficient 0.0034, Std Err = 0.0262 … t ~ 0.1307 (no significance, random)
It doesn’t explain why there has been no increase in global temperature, lower troposphere or land ocean, over the last 8 years?
Why? If the energy from El Nino comes from deep-ocean currents, we would have to measure those deep-ocean temperatures (as KeithT noted above) to detect an energy decrease. But we wouldn’t necessarily expect an energy decrease in the deep ocean to show up as a temperature drop in the land-ocean surface temperatures.
We appear to still be sticking on this same point of misleading phrasing.
“The increasing values since the most recent spike have not exceeded the spike value” != “there has been no increase”.
Based on an enthalpy basis do you want explain how temperatures at “ocean depths” contribute to the upper surface temperatures. Do you know what the temperatures are in the oceans at “depths?”
What do you mean by spike? Did someone artifically create this spike? Where did the energy come from for this spike? Plus, the temperatures haven’t even exceeded the “spike” less 0.200 C.
My assumption is that an el nino would be a failure (or rather a temporary decrease) in a heat transfer mechanism from the actively solar heated surface to colder, deeper currents. Not really an explanation per se but at least the signs are right.
What is magical about 1998 for you though?
That’s putting it mildly. I’m just trying to follow the subject, and I have no idea why this thread is going in circles over such a simple issue.
As I understand it (and note that IANAOceanographer), periodic upwelling from the comparatively cold thermocline cools the comparatively warm ocean surface (as well as providing it with nutrients). When the thermocline is depressed, this upwelling is less efficient, so the upper waters stay warmer and the lower waters stay colder, and you get an El Nino. Hence the ocean surface and atmosphere temperatures are warmer than they ordinarily would have been.
Sez here that in the thermocline, water temperatures drop about 20 degrees Celsius with each additional 150 meters of depth; below the thermocline, temps are close to freezing.
I thought I already answered this. A data spike is, as I said, “an isolated outlying value” that doesn’t follow the general trend of the data.
No. Data spikes can be due to a number of causes: for example, when a brief surge in one of the data inputs temporarily overwhelms the others. That is what is thought to have happened in the case of the 1998 temperature spike, where the unusually warm ocean-surface temperatures caused by the El Nino effect briefly forced up the global temperature values before dropping back into their normal pattern after 1998.
From the unusually warm ocean-surface temperatures in the El Nino years, caused by the unusual absence of surface cooling from deep-ocean upwelling.
I’m sorry, but it seems I’ve been explaining the same things over and over here. Could you tell me what part of this isn’t clear?