New paper: Global sea level linked to global temperature

Global sea level linked to global temperature
By Martin Vermeera, and Stefan Rahmstorf
October 26, 2009
http://www.pnas.org/content/106/51/21527.full.pdf

This new paper takes a 'modern' look at sea level rise projections out to 2100 AD.

The abstract notes:
"For future global temperature scenarios of the Intergovernmental Panel on Climate Change’s Fourth Assessment Report, the relationship projects a sea-level rise ranging from 75 to 190 cm for the period 1990–2100"

In the discussion on projections of future sea levels:-
"Qualitatively we consider this decline in the thermal share and increasing importance of ice melt a robust result, which is our key difference to the IPCC AR4 (2), where the ice-melt share is assumed to diminish with thermal expansion contributing between 55% and 70% of the total sea-level rise over the 21st century."

which fits well with my albeit uneducated perspective,

In
Discussion: Implications for the Future
If our method presents a reasonable approximation of the future sea-level response to global warming, then for a given emission scenario sea level will rise approximately three times as much by 2100 as the projections (excluding rapid ice flow dynamics) of the IPCC AR4 (2) have suggested. Even for the lowest emission scenario (B1), sea-level rise is then likely to be [about] ~1 m; for the highest, it may even come closer to 2 m.

Uncertainties remain, however..."

The discussion concludes:

"In addition, highly nonlinear responses of ice flow may become increasingly important during the 21st century. These are likely to make our linear approach an underestimate. Therefore, we have to entertain the possibility that sea level could rise faster still than suggested by the simple projection based on Eq. 2.

How much faster? Pfeffer et al. (25) provided an independent estimate of maximum ice discharge based on geographic constraints on ice flow; they concluded that sea-level rise in the 21st century is very unlikely to exceed 200 cm. If this estimate is correct, a nonlinear dynamical ice-sheet response may not change our estimate upward by very much. To limit global sea-level rise to a maximum of 1 m in the long run (i.e., beyond 2100), as proposed recently as a policy goal (26), deep emissions reductions will be required. Likely they would have to be deeper than those needed to limit global warming to 2 °C, the policy goal now supported by many countries. Our analysis further suggests that emissions reductions need to come early in this century to be effective.""

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and still...
ftp://ftp.cmdl.noaa.gov/ccg/co2/trends/co2_mm_mlo.txt
Seasonally corrected March 2010 level of CO2 = 389.44ppm, and so based on the average rate of change over the last three months, its probably about 389.73ppm today, and still rising....

A Good Hard Look at the Science of Climate Change

The Economist in a leader:
http://www.economist.com/opinion/displaystory.cfm?story_id=15720419

and article:
http://www.economist.com/opinion/displaystory.cfm?story_id=15719298

published in March 2010 has had come out with a very balanced view of the current state of the way the science about climate change is done. Well worth a read.

In its final paragraph the article says:
"The fact that the uncertainties allow you to construct a relatively benign future does not allow you to ignore futures in which climate change is large, and in some of which it is very dangerous indeed. The doubters are right that uncertainties are rife in climate science. They are wrong when they present that as a reason for inaction. "

The leader concludes:

"With climate change you do not need to invent things; the truth, even with all those uncertainties and caveats, is scary enough."

and still...
ftp://ftp.cmdl.noaa.gov/ccg/co2/trends/co2_mm_mlo.txt
Seasonally corrected March 2010 level of CO2 = 389.44ppm, and rising....

CO2 levels at Mauna Loa. A great indicator of how well we are doing (or not!).

I have put this link in the sidebar link list, but its worth showing you what it does.

The chart gives a monthly update of the CO2 levels at Mauna Loa - probably the most iconic (and certainly the longest running) CO2 monitoring site.

Chart: CO2 level at Mauna Loa. Data up to February 2010.

As you see there are seasonal variations (due mainly to plant growth during the northern hemisphere summer absorbing more CO2), so the 'middle' line in the chart is the level with the seasonal variation removed.

Make a note in your calendar to check this each month.

I've been watching this for a while, and in spite of all the cries of denial and hope we haven't made the overall trend line turn downwards yet.

Until we do; (you know what I'm going to say don't you) the ice is going to continue to melt and the seas will continue to rise until all the ice is gone.

Admirable restraint and a state of denial?

http://www.gosford.nsw.gov.au/gis/slr/documents/sea_level_rise_facts.pdf

It is great to see some places taking sea level rise seriously.

This council in New South Wales has made a determination of sea level rise expected by 2100, and is hanging its policy-hat thereon.

"At its meeting of 27 January 2009, [Gosford City] Council considered and approved a report that recommends adopting, for purposes of future planning, a sea level rise planning level of 91cm by the year 2100."

The 91cm figure is made up of

59cm from the IPCC's AR4 global average sea level rise (ignoring ice melt) - high emissions scenario

20cm from AR4's allowance for ice melt uncertainty

and

12cm from the local CSIRO Technical Report (2007) – calculation for local variation on IPCC global average sea level rise.

The key uncertainty of course is the value for the 'ice melt uncertainty'.

Quite understandably the council is using the most solid data it can find, and that is the well-reviewed IPCC AR4 report. But as other postings have shown here, science and the ice has moved on quite a bit since 2007.

Thus I suggest that the council is doing well in that it is adopting figures that are very unlikely to be proven wrong (if we say that it will get at least as high as they say). They could have plugged for a higher figure (say +1.5 metres) without much chance of being wrong either, but they exercised admirable restraint by sticking to the IPCC values.

The national Real Estate and Insurance councils are of course panic-stricken by even this modest 91cm figure as it impacts directly on values and insurance costs.

The Property Council of Australia made a submission to the council including:-
http://www.propertyoz.com.au/Article/Resource.aspx?p=21&submission=551

"We have strongly advocated that the NSW Government demonstrate that it has considered and understands how sea level rise and the proposed projections will impact the property sector and broader community.

As an example, the Government must consider insurance implications and the likely response from the insurance sector as a result of revised sea level projections being released. This includes access to and the risk rating/cost of insurance.

A further worrying example relates to the values of property now caught within any area mapped as being at risk of inundation from rising sea levels. This will have severe flow on financial consequences for the and result in a reduction in lender’s loans to value ratio on property in this category."

The property council's points are well made, but I think from the wrong direction. They would like to see the council adopt a lower sea level rise prediction so that the financial impacts will be avoided. They do not argue the science. They do not suggest that the 91cm is wrong, just that they do not want to accept the consequences of sea level rise at all. Therein lies a state of denial.

As far as I can discern the City Council's resolution of 27 January 2009 embodying a sea level rise of 91cm by 2010 still stands. Good on ya mates!

Greenland Ice Sheet Losing Ice Mass on Northwest Coast, Says New International Study

http://www.colorado.edu/news/r/f595fae00e6b451d4016ab9a43a049f8.html

Greenland Ice Sheet Losing Ice Mass on Northwest Coast, Says New International Study

March 23, 2010

"When we look at the monthly values from GRACE, the ice mass loss has been very dramatic along the northwest coast of Greenland," said CU-Boulder physics Professor and study co-author John Wahr, also a fellow at CU-Boulder's Cooperative Institute for Research in Environmental Sciences.

"This is a phenomenon that was undocumented before this study," said Wahr. "Our speculation is that some of the big glaciers in this region are sliding downhill faster and dumping more ice in the ocean."

"If this activity in northwest Greenland continues and really accelerates some of the major glaciers in the area -- like the Humboldt Glacier and the Peterman Glacier -- Greenland's total ice loss could easily be increased by an additional 50 to 100 cubic kilometers (12 to 24 cubic miles) within a few years," said Khan.

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NJW Comment: If it looks like a dog, barks like a dog... !