Slowing Sea Level Rise Projections

NOAA Sea Level New York City

NOAA Sea Level New York City

In recent years there have been several projections regarding sea level rise, including claims that the oceans could rise up to 10 feet by 2100.  It is time to consider just how much weight we should give these projections as they would suggest that vast areas of the world’s coastline could be flooded before there was time to fully react.

What we know

Global warming
As per the National Oceanic and Atmospheric Administration (NOAA), the global temperatures are rising at a rate of about .07C per decade (0.7C per century) and currently are about 0.8C higher than around 1900. The warming has not been continuous; however, as there was a cooling trend between 1880 and 1910 followed by a moderate warming of about 0.25C from about 1910 to 1945.  Temperatures remained stable or possible cooled slightly between 1945 until about 1978 followed by another period of stronger warming of about 0.6C from 1978 to present.

NOAA Global Surface Temperature Anomaly

NOAA Global Surface Temperature Anomaly

 

 

 

 

 

 

 

 

Sea Levels
During the 20th Century, sea level rose at a rate of about 1.8 mm/yr based on actual tide gages.  More recent data based on satellite observations suggests, however, that since 1993 the rate was between 2.9 mm/yr and 3.4 mm/yr.

The accuracy of direct sea level measurements via satellites is about +/- 2 cm (20 mm) so we may need more time to judge the accuracy of the trends calculated from these measurements vs. those made from long-term tide gage observations.  See: Sea Level Trends – NOAA Tide and Currents page 

Studies of sea level rise rates during the past century suggest that short-term (18-yr trends) of sea level rise rates have ranged between 0 and 4 mm/yr, even prior to 1950 (before most of   CO2 was added to the atmosphere). This suggests that the current higher rates may not be solely driven by greenhouse gas emissions and adds uncertainty to the various sea level projections.

18 year sea level rates

18 year sea level rates

Source:  Is sea level rise accelerating? Judith Curry Blog post February 23, 2016

The Future

Bottom line, sea level is rising and the rate has increased but there is significant uncertainty regarding predicting future rates and thus sea level estimates for the next 50-100 years are  problematic.  If the rate of sea level rise would double, for example, over the next century from the current satellite estimates, we would expect a total sea level rise of about 1.2-1.4 ft. by 2100

By contrast, global sea level rose by a total of about 120 meters over a period of about 8,000-9,000 years as the vast ice sheets of the last glaciation melted away. This equates to an average rate of sea-level rise during this period of roughly 1 meter (3.3 feet) per century or about 10mm per year (Some studies suggest the rate was up to 13 mm per year). Even if somehow we could get to the rates encountered after the last glaciation of 10-13 mm/yr over the next century then by 2100, the total rise will be about 1.8-2.2 feet.

So then the question is how could we get to a 6 to10 foot sea level rise so quickly?  A recent study suggests that a rapid collapse of the Western Antarctic Ice Sheet is possible. The western half of the Antarctic has its base lying below sea level so as global temperatures rise; warmer ocean water will melt the underside of the ice sheets.

The modeling suggests significant sea level rise is possible from Antarctica ice melt alone by 2100.  The key assumption here is that greenhouse gas emissions will boost the planet’s temperature by about 4 degrees C (7 degrees F) which is considerably more than the present 0.8C of observed warming.  The paper admits that under the model the timing and pace of Antarctica’s ice loss is “really uncertain”.

Without the vast continental ice sheets of the last glaciation, it is doubtful that we will reach the extreme prediction of  up to 10 feet. In order to see a sea level rise of 10 ft by 2100, the average annual rise would have to be about 37 mm/yr, more than 10 times the  current rate!.   In addition, these new estimates are also far above the estimates by the Fifth Assessment Report from the United Nations’ Intergovernmental Panel on Climate Change.  Here, they claim that the most likely amount of global sea level rise would be about 1 foot to slightly more than 3 feet by 2100.

Fred Pickhardt
Ocean Weather Services.

 

 

 

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TC Donna Update

TC Donna Satellite Image

TC Donna Satellite Image

TC Donna located over the South Pacific about 337 NM northwest of Port Vila, Vanuatu currently has maximum winds of about 85 knots with hurricane force winds extending outward about 25 NM from the center. Maximum significant wave height is estimated to be about 24 feet (7.3 meters).  Forecast track takes Donna south then southeast with maximum winds peaking  at about 100-110 knots during the next 18-24 hours before a weakening trend begins.

 

Updated Forecast Track

 

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Tropical Cyclone Donna strengthens over South Pacific

Satellite image TC Donna

Satellite image TC Donna

Tropical Cyclone Donna over the South Pacific was located about 298 NM N-NE of Port Vila, Vanuatu and was moving towards the west at about 9 knots. Conditions are favorable for development as Donna is currently over warm 30C sea temperatures with low atmospheric shear.  Forecasts suggest Donna will reach a peak of wind speed of 105-115 knots during the next 72 hours. A turn towards the southwest then south is expected during the next 48 hours then more towards the southeast.  Donna is a threat to the islands of Vanuatu.

Updated Forecast Track 

 

 

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TC 17S develops N-NW of Darwin

Satellite image via JTWC

Satellite image via JTWC

TC 17S  has developed about 179 NM NNW of Darwin Australia and was moving towards the SW at about 8 knots with max winds of about 35 knots.

Conditions favor some slow deepening over the next 24-36 hours then unfavorable conditions will cause the system to weaken and then dissipate in about 4 days.

 

Forecast Track:

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TS Arlene named over North Atlantic

NHC Forecast Track

NHC Forecast Track

A sub-tropical low over the central North Atlantic has been classified by the National Hurricane as the season’s first Tropical Storm and has named it Arlene with max winds of about 40 knots.  Arlene is over fairly cold SST of about 19C so it is unusual to see this type of transformation.  In any case, Arlene will move towards the WNW and will be absorbed into a larger extra-tropical low to the west fairly quickly.

NOAA Satellite image TS Arlene over cold SST

NOAA Satellite image TS Arlene over cold SST

 

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Storm low over the south-central North Atlantic

NOAA OPC Surface Analysis

NOAA OPC Surface Analysis

A deep 987mb low over the central North Atlantic at 33N latitude is producing winds 35-50 knots with seas to 34 feet (10.4 meters) west of the center.  The low is forecast to slowly drift towards the southeast and gradually weaken.

This system may affect some shipping bound for the US Gulf and Caribbean ports.

NOAA OPC Sea Height Analysis and Satellite photo

NOAA OPC Sea Height Analysis and Satellite photo

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TC Cook threatens New Caledonia

TC Cook IR satellite image

TC Cook IR satellite image

TC Cook, as of 1500 UTC 09 April was centered about 225 NM north of Noumea, New Caledonia in the South Pacific and was moving towards the southwest at about 7 knots.  Currently max winds are estimated at 70 knots and the forecasts suggest max winds could reach 90-100 prior to making landfall on the island of New Caledonia near 1200 UTC April 10th.

Latest track forecast 

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TC Ernie Update

TC Ernie IR Satellite Photo

TC Ernie IR Satellite Photo

TC Ernie deepened rapidly during the past 24 hours and as of 1800Z April 17th was about 435 NM N-NW of Learmonth, Australia and was moving towards the S-SW at 2 knots.  Max winds are estimated to be 130 knots with a max significant wave height of 41 feet (about 12.5 meters).  A turn towards the southwest, later west is forecast as well as gradual weakening after 12-24 hours.

 

Latest Forecast Track

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TC Ernie Deepens over Southern Indian Ocean

TC Ernie IR Satellite view

TC Ernie IR Satellite view

April 6th 2100Z:  TC Ernie over the southern Indian Ocean was located about 511 NM N-NW of Learmonth, Australia was moving towards the S-SW at about 7 knots with max winds of at least 40-45 knots, however, recent satellite images suggest it may already be nearing hurricane force. Forecast is for Ernie to continue to deepen for the next 24 hours followed by gradual weakening after about 48 hours.                                                                                                                    Latest Forecast Track

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Large Hurricane Force Storm over North Atlantic

NOAA OPC 1200 UTC Surface Analysis

NOAA OPC 1200 UTC Surface Analysis

A Hurricane force North Atlantic low is producing winds of 50-65 knots and seas to 43 feet between 90NM and 360NM southwest of the center.  Likely will cause delays to westbound traffic bound for the US East Coast.

NOAA Satellite Photo

NOAA Satellite Photo

NOAA OPC Wave Height Analysis

NOAA OPC Wave Height Analysis

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