Originally posted by Kali74
reply to post by talklikeapirat
Or you can use the same site and input the full span of years so they're all in one graph which shows a more accurate picture in my
An accurate picture of what? The "anthropogenic signal"? All it shows is, that according to GIStemp, global mean temperature has increased by
0.88°C in the last 100 years.
The IPCC's own assessment is, that human influence became the dominant climate factor in the mid 20th century, when greenhouse gas emissions started
to increase exponentially.
Hansen & Sato
Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic
greenhouse gas concentrations. This is an advance since the TAR’s conclusion that “most of the observed warming over the last 50 years is likely
to have been due to the increase in greenhouse gas concentrations”.
Nathan's calculations are not based on IPCC estimates for climate sensitivity, but rather on the ~1°C according to the Boltzmann law. But
EasyPleaseMe has raised an interesting point.
That's simply incorrect. The IPCC has never projected a set value of temperature increase.
Of course it has. Why would you even claim it hasn't? That's the whole point of the exercise. To provide assessments of future climate projections
It is extremely likely [">95% probability"] that human activities have caused more than half of the observed increase in global average surface
temperature since the 1950s.
Naturally, the logical questions would be, how much has it warmed and how much warmer does it get in the future. Contrary to your claim, the IPCC has
given very specific answers.
The right-hand panel shows ranges of global average temperature change above pre-industrial, using (i) ‘best estimate’ climate sensitivity
of 3°C (black line in middle of shaded area), (ii) upper bound of likely range of climate sensitivity of 4.5°C (red line at top of shaded
area) (iii) lower bound of likely range of climate sensitivity of 2°C (blue line at bottom of shaded area).
The "set values" for each of the different climate scenarios are even more specific. It's only reasonable to test these model projections against
reality. Which is exactly the point von Storch is making, or
and ironically it is exactly what has been done in
the article you've linked to. Play around with the GISS time series and you will find that most of the warming in last two decades occured in 1990's
and as shown above, temperature trend post 2000 has been virtually flat.
has done it too, and got it
The linear global warming trend since 2000 is 0.18°C per decade for the IPCC model mean, vs. 0.15°C per decade according to GISTEMP (through
mid-2011). This data falls well within the model uncertainty range (shown in Figure 2, but not Figure 3), but the observed trend over the past decade
is a bit lower than projected.
The linear global warming trend since 2000 according to GISTEMP has been closer to 0.08°C vs. SkepticalScience's claim and
vs. the IPCC model mean. It shows even less warming through mid-2013 and is approaching a trend 4 times smaller than climate models project. A value
Ensembles with different modifications to the physical parameters of the model (within known uncertainties) are performed for several of the IPCC
SRES emissions scenarios. Ten of these simulations have a steady long-term rate of warming between 0.15° and 0.25ºC decade–1, close to the
expected rate of 0.2ºC decade–1 (...).
Near-zero and even negative trends are common for intervals of a decade or less in the simulations, due to the model’s internal climate variability.
The simulations rule out (at the 95% level) zero trends for intervals of 15 yr or more, suggesting that an observed absence of warming of this
duration is needed to create a discrepancy with the expected present-day warming rate.
As for the cheap shots against von Storch, it would have taken you less than a minute to find the link, listing him as
lead author for AR5
. He's a accomplished climate scientist. That's it.