If autocorrelation is taken into account, then the significance becomes much smaller; or equivalently, the confidence bounds on trend become larger.

This means that 16 years is too short a time to say anything much about trend simply from the temperature data. To say “no significant warming” invites confusion; the real situation is there is no significance for telling *what* the trend is doing.

In particular, you can’t conclude with any confidence that the warming has paused, or stopped, or even changed.

The solution to this is to use a longer period of time, in which case you *do* get significance… and it *is* warming. But if you are specifically interested in the last 16 years, then you either have to say “too short a time to say much of anything”, or you have to get more data about the sources of short term variation.

If you stick with just the available temperature data, then you can’t conclude cooling or pauses with any confidence, because the significance does not allow for it.

If you go on to look at sources of variation — which include greenhouse effects, ENSO and volcanic effects, and separate them out, then the data DOES allow you to conclude that the warming is continuing over the last 16 years with very good significance indeed.

Excuse me for being skeptical… but what data are you using?

Over the last 16 years, through the end of 2012, the 16 year trend from HadCrut4 is 0.054 C/decade +/- 0.037

That is 95% confidence limits using convention linear regression and monthly data points with global anomalies.

The GISS data set gives 0.080 C/decade +/- 0.039

So no, I think that the data DOES show a statistically significant positive warming trend over 16 years.

Claims to the contrary by all the usual suspects notwithstanding. The data is there; look at THAT. It does show a statistically significant warming trend over 16 years.

BTW, 16 years too short to tell you the longer term trend. The 16 year trend, no matter what value it shows, reflects a lot of short term variation that obscures the longer trend. Much of the online discussion of this denialist talking point has focused on identifying those short term influences that impact trends over these short time spans.

But be that as it may; the data really does show warming over 16 years to the end of 2012.

As for decades (an even shorter period) with a definite negative trend, that’s just “going down the up escalator”.

What makes the short-range version of Hoyle & wickramasinghe’s old hypotheis problematic is that ballistics is a two way street ( Happy gun day by the way – pity nobody organized a post-boxing day shoot .) .

The same hypervelocity asteroid fragments that whack bits of Mars int the inner solar system to fall to Earth as shergottites srtike divots off its surface and into the outer solar system as well.

The odds on them hitting Mars are deeply discounted by the reversal of outbound accelerstion by the sun’s gravity, but since the time scale is astronomical, such things will and do happen, albeit as rarely as catastrophic asteroid impacts .

If eevery earthly astrobleme represents a scatter shot of terrestrial debris in Mar’s general direction, we can expect inverse-shergottite meteorites ( what to call them ? the mineralogists have already pinched ‘tellurites’ ) to be only a few orders of magnitude rarer on Mars than here.

So ballistics being blind, some few bits of terrrestrial material deposited on Mars in the last few billion years may already have been Returned To Sender by the impact pf near-Mars asteroids. Calculating the fraction that contain diatom fossils is best left to a bar-full of soft rock geologiists at an AGU meeting.

Incidentally, I devoted an op-ed to this conundrum back in the day when the WSJ still had a science editor:

http://online.wsj.com/article/SB111050427890376787.html

http://vvattsupwiththat.blogspot.com/

“One should also remember the pages of drivel written about super-cold anarctic temperatures and CO2 snow”

Beat me to it, good on you! I’ll add that the best part about that post and the string of comments centers around Watts’ speculating that all standard texts on physical chemistry are wrong, Steve Goddard right …