The Coming 'Instant Planetary Emergency'.

[Uncle Joe]

57. Yes they have a track record but it has been on the conservative side as you stated.

In regards to sea level rise they've already revised their 2004 IPCC Report to a more negative outlook.

http://www.realclimate.org/index.php/archives/2013/10/sea-level-in-the-5th-ipcc-report/



For an unmitigated future rise in emissions (RCP8.5), IPCC now expects between a half metre and a metre of sea-level rise by the end of this century. The best estimate here is 74 cm.

On the low end, the range for the RCP2.6 scenario is 28-61 cm rise by 2100, with a best estimate of 44 cm. Now that is very remarkable, given that this is a scenario with drastic emissions reductions starting in a few years from now, with the world reaching zero emissions by 2070 and after that succeeding in active carbon dioxide removal from the atmosphere. Even so, the expected sea-level rise will be almost three times as large as that experienced over the 20th Century (17 cm). This reflects the large inertia in the sea-level response – it is very difficult to make sea-level rise slow down again once it has been initiated. This inertia is also the reason for the relatively small difference in sea-level rise by 2100 between the highest and lowest emissions scenario (the ranges even overlap) – the major difference will only be seen in the 22nd century.

(snip)

The range up to 98 cm is the IPCC’s “likely” range, i.e. the risk of exceeding 98 cm is considered to be 17%, and IPCC adds in the SPM that “several tenths of a meter of sea level rise during the 21st century” could be added to this if a collapse of marine-based sectors of the Antarctic ice sheet is initiated. It is thus clear that a meter is not the upper limit.

(snip)

4. Greenland might melt faster than current models capture, due to the “dark snow” effect. Jason Box, a glaciologist who studies this issue, has said:

There was controversy after AR4 that sea level rise estimates were too low. Now, we have the same problem for AR5 [that they are still too low].

Here's more from the IPCC regarding methane release from fracking.

http://thinkprogress.org/climate/2013/10/02/2708911/fracking-ipcc-methane/

The Intergovernmental Panel on Climate Change (IPCC) reports that methane (CH4) is far more potent a greenhouse gas than we had previously realized.

This matters to the fracking debate because methane leaks throughout the lifecycle of unconventional gas. Natural gas is, after all, mostly methane (CH4).

We learned last month that the best fracked wells appear to have low emissions of methane, but that study likely missed the high-emitting wells that result in the vast majority of methane leakage. Back in August, a NOAA-led study measured a stunning 6% to 12% methane leakage over one of the country’s largest gas fields — which would gut the climate benefits of switching from coal to gas.

(snip)

But the IPCC’s latest report, released Monday (big PDF here), reports that methane is 34 times stronger a heat-trapping gas than CO2 over a 100-year time scale, so its global-warming potential (GWP) is 34. That is a nearly 40% increase from the IPCC’s previous estimate of 25.

With developments like this I believe the IPCC will be revising their reports again and not for the better.

Having said that even under your scenario it's not going to be "business as usual."