The seas are rising, and have been over ten thousand years. What comes next?

Summary: The world has been warming for the past two centuries, and the oceans have been rising for over ten millenia. The urgent task of climate scientists is to determine if these trends will accelerate, and if so by how much and when. Here we look at the history of rising seas, and what the new IPCC report warns us to expect. Rising seas are one of the most vivid and potentially most important of the climate changes expected during the 21st century.


Here are other posts in this series about second order draft (SOD) of the Fifth Assessment Report (AR5) by the Intergovernmental Panel on Climate Change (IPCC).

And this from earlier reports: When did we start global warming? See the surprising answer (it’s not what you’ve been told).



  1. Introduction
  2. Long-term sea levels, based on proxy data
  3. The past century (direct measurements,
    moderately reliable)
  4. Recent (reliable direct measurement)
  5. IPCC forecasts of the future
  6. For More Information about rising sea levels

About measurements: one inch = 25 mm = 0.025 meter

(1) Introduction

In this series we look at the latest work of the IPCC to see what the news media have hidden from us about the results of climate scientists. The world has been warming for two centuries, as all agree. But so much else they’ve told us is not accurate. Mostly due to their exaggerations, misrepresentations and omissions of the IPCC’s work — and the peer-reviewed literature on which it rests.

As we see in the comments to previous posts, this produces odd situation — increasingly common in today’s New America, with its broken OODA loop — of well-educated people astonished to learn what climate scientists have said for many years — because during that time they’ve read quite different things in the news media. Show them the text, the data — and watch the resulting incredulous shock.

The same process will happen the Right, as those on they (eg, the Tea Party) learn they rely on sources that lie to them. The surprise 2012 election results might have started this process. The results of these collisions between facts and dogma will play a large role in determining the fate of 21st century America.

Now, let’s turn to the seas. First we’ll look at sea levels over various time horizons. Then we’ll look at the latest IPCC report.

(2) Long-term sea levels, based on proxy data

From “Sea-level fluctuations during the last glacial cycle“, M. Siddall et al, Nature, 19 June 2003 — Gated.

Nature, 19 June 2003


(3) The past century (direct measurements, more reliable)

From the EPA’s Climate Change Indicators page:


From the EPA "Climate Change Indicators" page
From the EPA “Climate Change Indicators” page

(4) Recent data (reliable direct measurement)

From the University of Colorado Sea Level Research Group:

U CO Sea Level Research Group

(5) IPCC forecasts of the future

The AR5 forecasts a sea level rise of from 0.5 to 1 meter (20 to 40 inches) over the next 90 years (see the graphs below). For the extreme scenario, the rate of rise will accelerate so that arox 2/3 of the rise occurs after 2050 (so that we’ll have response time after we confirm the accelerating rise).

(a) About the scenarios: from the Technical Summary – Thematic Focus Element 8

Future anthropogenic emissions of greenhouse gases, aerosol particles and other forcing agents such as land use change are dependent on socio-economic factors including global geopolitical agreements to control those emissions. … In this report, outcomes of simulations that use the new scenarios referred to as “Representative Concentration Pathways” (RCP). {these replaced the “Special Report on Emissions Scenarios” (SRES) used in the previous report (AR4)}

(b) From the Executive Summary of Chapter 13: Sea Level Change:

Paleo sea level records from warm periods during the last 3 million years provide medium-to-high confidence that global mean sea level was more than 6 meters {20 feet} higher than present when global temperature was 2°C–3°C warmer than present.

… It is very likely that the rate of global mean sea level rise during the 21st century will exceed the rate observed during 1971–2010 for all RCP scenarios.

For the period 2081 to 2100, compared to 1986 to 2005, global mean sea level rise is likely to be in the range 0.29–0.55 meters {11 – 22 inches} for RCP2.6 {to} … 0.56–0.96 meters {22-38 inches} by 2100 for RCP8.5.

Unlike in the AR4, these projections include a contribution from changes in ice-sheet outflow, for which the central projection is 0.11 meter {4 inches}. There is only medium confidence in these ranges of projected global mean sea level rise, because there is only medium confidence in the likely range of projected contributions from models of ice sheet dynamics, and because there is no consensus about the reliability of semi-empirical models, which give higher projections than process-based models. Larger values cannot be excluded, but current scientific understanding is insufficient for evaluating their probability.

… It is very likely that there will be an increase in the occurrence of future extreme sea level and flooding events. The combined effects of mean sea level rise and changes in storminess will determine future extremes. …

Figure 13.9: Projections from process-based models of (a) GMSL rise relative to 1986–2005:


(6) For More Information: other posts about rising sea levels

  1. An example of important climate change research hidden, lest it spoil the media’s narrative, 22 May 2009 — About rising sea levels
  2. About that melting arctic ice cap, 17 April 2010
  3. Fear or Fail: about the melting Greenland ice sheet, 24 May 2010
  4. Today’s good news, about rising sea levels, 3 June 2010 — Esp note the links to articles and studies!
  5. More about the forecast for flooded cities in the late 21st century, 16 October 2010
  6. Looking into the past for guidance about warnings of future climate apocalypses, 17 October 2010 — Two of James Hanson’s past predictions
  7. About the coming sea ice Armageddon!, 19 June 2012
  8. Shaping your view of the world with well-constructed propaganda, 21 June 2012 — About rising sea levels.
  9. Run from the rising waves! (The latest climate catastrophe scare), 27 June 2012



7 thoughts on “The seas are rising, and have been over ten thousand years. What comes next?”

    1. DonP
      You would be right for cm measures. Here is about mm. 1m=100cm, 1m=1000mm hence inch=0.025m from 25mm / 1000mm= 0.025m

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