Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 



Forgot your password?
typodupeerror
Check out the new SourceForge HTML5 internet speed test! No Flash necessary and runs on all devices. ×

Comment Re:Tiny sample size, evolving measurement methodol (Score 2) 369

We have various lines of evidence going back thousands of years which suggest quite strongly that it hasn't been as hot on average as it is now for at least 120 000 years, and for the previous 5 decades, each decade has been on average hotter than the previous one.

We have a physical mechanism which even in relatively simple modelling predicts such a rise quite convincinglyn, and in more sofisticated models which include unpredictable events like volcanic eruptions manage to reproduce the climate of the last 100+ years very very well starting from first principles (not statistic curve-fitting as some would want you to believe)

We have direct temperature series going back much further than 134 years, only they're local, not global, still, they show that the current circumstances are pretty much unprecedented as far back as we can measure.

It's not because we don't know everything that we know nothing...

Comment Re:All the way back to... (Score 1) 369

We have various lines of evidence going back thousands of years which suggest quite strongly that it hasn't been as hot on average as it is now for at least 120 000 years, and for the previous 5 decades, each decade has been on average hotter than the previous one.

We have a physical mechanism which even in relatively simple modelling predicts such a rise quite convincinglyn, and in more sofisticated models which include unpredictable events like volcanic eruptions manage to reproduce the climate of the last 100+ years very very well starting from first principles (not statistic curve-fitting as some would want you to believe)

We have direct temperature series going back much further than 124 years, only they're local, not global, still, they show that the current circumstances are pretty much unprecedented as far back as we can measure.

It's not because we don't know everything that we know nothing...

Comment Re:NASA ignoring satellite measurements... (Score 3, Informative) 369

1) Satellites don't measure the same thing as ground thermometers (satellites measure the lower troposphere in its entirety, surface thermometers measure the surface temp) so it's not entirely unsurprising they don't give identical numbers to within an error margin.

2) Satellites don't measure polar temperatures very well, and polar amplification makes the temps at particularly the north pole go up faster than average - so a lower total response from the satellite data is expected.

3) People are freaking out over minor adjustments to the surface record which are well-supported by evidence (for example corrections made for a change in the time-of-day of the measurements at some stations at some point, or stations moving from city-centers to airports outside the city center) but the whole satellite record itself is full of far bigger corrections, the raw data of the satellites isn't a directly measured temperature but a remote sensor reading, which is influenced by a whole bunch of internal (sensor drift) and external (observation angle, satellite orbital height, weather conditions) factors. It's almost a miracle that they manage to get a useful data-series out of these satellite sensors.

Honestly, the only reason deniers try to argue that the satellite record is "more accurate" is because it shows a higher peak in 1998 and less total warming, allowing them to fiddle with the results to make it appear there's no warming at all - except that nowadays even the satellite record no longer supports that conclusion.

Comment Re:Evidence of the Great Filter? (Score 2) 365

We can get some idea of the likelihood of some stages by looking at how long in took for them to occur on earth. For instance, it took about 1 billion years for life to form on earth, but after that it took an additional 3 billion years before the Cambrian Explosion, where we saw significant diversification of complicated lifeforms. That 3 billion year gap allows time for all sorts of global cataclysms--we had one that nearly wiped out life during the snowball earth. After the Cambrian Explosion it took a mere half billion years to reach technological intelligence.

But it's very dangerous to simply extrapolate from a single data point (Earth) - there are quite a few environmental elements that could massively influence those timescales - for example the early sun was quite a bit fainter than it currently is, so those 3 billion years might just have been necessary to reach some kind of tipping point favouring the development of complex multicellular life, on another planet under slightly different conditions, this might take just a fraction of that time (or it might never reach that tipping point) - similarly, it took about half a billion years to reach technological intelligence, but that may just be due to particular circumstances on our world, the timing, place and cause of the different mass extinctions, the conditions occuring which permitted the different precursor steps that may be required for a technological civilisation to occur (things like the move from water to land, the increase in available energy afforded by endothermy, ...)

Comment Re: They're called trees. (Score 4, Informative) 128

The sun is _slowly_ brightening - this is happening on timescales of tens to hundreds of millions of years. The fact that CO2 was significantly higher tens or hundreds of millions of years ago is not super-relevant to today's conditions, but it helped keep temperatures bearable in the distant past, when the sun was fainter. We are adding CO2 at a rate that is essentially instantaneous compared to the effects of this solar evolution, they are even still extremely quick on the much shorter (tens of thousands of years) timescales of the Milankovitch-cycles (which are the orbital cycles which are the underlying cause of our glacial-interglacial variation in the past few million years)

What interests us at this time is what we are doing to our atmosphere over a period of tens to hundreds of years, and what effect that has on timescales of tens, hundreds and thousands of years - even if we humans stop all of our CO2 emissions (except breathing of course), the increased concentration versus "before" will be considerable thousands of years into the future, as will the effects of that increase on climate.

So stating "still at the extreme lower end of historic levels" is technically correct, but practically misleading, as it suggests there's nothing wrong with CO2-levels.

Comment Re:Neutrino Detection? (Score 2) 85

Yes, neutrinos have been detected in this type of detector for many, many years - in 1987 the neutrino's from SN1987A were detected by several of these detectors.

See
http://en.wikipedia.org/wiki/Neutrino
and
http://en.wikipedia.org/wiki/SN_1987A

For the actual papers, consult the "sources" listing at the end of each Wikipedia entry.

Slashdot Top Deals

"More software projects have gone awry for lack of calendar time than for all other causes combined." -- Fred Brooks, Jr., _The Mythical Man Month_

Working...