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How much is sea level rising?

What the science says...

Select a level... Basic Intermediate

A variety of different measurements find steadily rising sea levels over the past century.

Climate Myth...

Sea level rise is exaggerated

"We are told sea level is rising and will soon swamp all of our cities. Everybody knows that the Pacific island of Tuvalu is sinking. ...

Around 1990 it became obvious the local tide-gauge did not agree - there was no evidence of 'sinking.' So scientists at Flinders University, Adelaide, set up new, modern, tide-gauges in 12 Pacific islands.

Recently, the whole project was abandoned as there was no sign of a change in sea level at any of the 12 islands for the past 16 years." Vincent Gray).

At a glance

You'd think it would be obvious, wouldn't you? If ice (or snow) melts, you get water. Water flows downhill through gravity and collects wherever it can be retained. In areas that see regular winter snowfalls, the processes involved are familiar. Snow-capped mountains look photogenic but along comes the eventual thaw and the river levels rise sharply with all the meltwater.

Now apply the same basic principles to glaciers and ice-caps. It should not come as a surprise that exactly the same thing happens and where that meltwater collects is ultimately the oceans. Note here that we're talking about land-based ice, not sea-ice: sea-ice is already part of the ocean so does not affect sea levels as it forms and melts every year. But melt enough land-ice and you get very significant change indeed.

What do we mean by very significant? Well, let's look at the transition out of the last ice-age that dominated the last 20,000 years. It began with ice-caps over parts of Europe and North America and ended not so long ago with much of that ice gone but with sea levels having risen by more than 120 metres. If that's not significant, what is?

There's not enough ice left on Earth to raise sea levels by that whopping amount now, but there is enough to raise the oceans by more than 60 metres. Over what sort of time-frame? Well, we know that the current rate of sea level rise is some 3.7 mm a year, or nearly an inch and a half per decade. A lot of that is due to the expansion of the oceans - as things are warmed up they expand. But the rate is accelerating. How fast do we think it can get? 

We do have the past to consider: during the glacial meltdown of the past 20,000 years, there was a period ominously named Meltwater Pulse 1A that began some 14,700 years ago. During this enhanced period of melting, sea levels rose by between 16 and 25 metres in about 400–500 years. That's roughly 40–60 mm per year or 16-23 inches a decade.

Could such drastic rates of sea level rise happen again? Probably not but nevertheless it shows what is possible as ice-sheets collapse in a warming world. But even if sea level rise stays at its current rate (it won't), that's getting on for a two-metre increase over the coming 300 years and a one-half to one-metre increase over the next 100 years. Now go anywhere affected by tides and think about all the communities of people that live and work along the shore. Pick the biggest spring tides, take a look at where they reach at high water, maybe watch the waves and surge when a storm occurs, then imagine an extra two metres of water on top of that.

And try to imagine being the decision-makers in the coming decades and centuries, who will have to work out what best to do. What would you think of the people all those years ago, who went around pretending this was not happening? Not favourably, for sure - because of such behaviour, that is how history will remember them.

Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!

Further details

The climate myth set out in the coloured box above gives an insight into the minds of climate change deniers. Why? Because it's entirely made-up. It annoyed the Realclimate blog's Gavin Schmidt sufficiently for him to write an eloquent debunking in 2012 that is well worth reading because it demonstrates so clearly what we, the scientific community, are up against.

The claim that tide gauges on islands in the Pacific Ocean show no sea level rise is nonsense: the data presented in the Realclimate link above show a variably rising sea level trend at each station. But what about global sea level rise?

Sea level rises as ice on land melts and as warming ocean waters expand. As well as being an existential threat to coastal habitation and environments (think about many of the world's capital cities here), sea level rise corroborates other evidence of global warming 

The black line in the graph below (fig. 1) clearly shows sea level is rising; its upward curve shows how sea level is rising faster as time goes on. The upward curve agrees with global temperature trends and with the accelerating melting of ice in Greenland and other places.

Because sea level behaviour is such an important signal for tracking climate change, the misinformers seized on the sea level record in an effort to cast doubt on this evidence. As fig. 1 clearly demonstrates, sea level bounces up and down slightly from year to year so it's possible to cherry-pick data and falsely suggest the overall trend is flat, falling or linear. You can try this yourself. Starting with two closely spaced data points on the graph below, lay a straight-edge between them and notice how for a short period of time you can create almost any slope you prefer, simply by being selective about what data points you use. Now choose data points farther apart. Notice that as your selected data points cover more time, the more your mini-graph reflects the big picture. The lesson? Always look at all the data rather than being fooled by selective presentations.

AR6 WGI Chapter 2 Figure 2_28c

Fig. 1: sea level change, from IPCC AR6 WGI Chapter 2 section Climate Change 2021: The Physical Science Basis. Tide-gauge and, more latterly, altimeter-based estimates since 1850. The full image with all four panels and IPCC caption is available here.

Other denialist arguments about sea level concern the validity of observations, obtained via tide gauges and more recently satellite altimeter observations.

Tide gauges must take into account changes in the height of land itself caused by local geological processes, a favourite distraction for deniers to highlight. It will come as no surprise to learn that scientists measuring sea level with tide gauges are aware of - and compensate for - these factors. Confounding influences are accounted for in measurements and while they leave some noise in the record they cannot account for the observed long-term upward trend.

Various technical criticisms are mounted against satellite altimeter measurements by deniers. Indeed, deriving millimetre-level accuracy from orbit is a stunning technical feat so it's not hard to understand why some people find such an accomplishment unbelievable. It's astonishing that in another breath they are happy to jump aboard an airliner, parts of which are engineered to a similar tolerance!

In reality, researchers demonstrate this height measurement technique's accuracy to be within 1 mm/year. Most importantly there is no form of residual error that could falsely produce the upward trend in observations. 

As can be seen in an inset of the graph in fig. 1, tide gauge and satellite altimeter measurements track each other with remarkable similarity. These two independent systems mutually support the observed trend in sea level. If an argument depends on skipping certain observations or emphasises uncertainty while ignoring an obvious trend, that's a clue you're being steered as opposed to informed. Don't be misled by only a carefully-selected portion of the available evidence being disclosed. Look at it all.

Current sea level rise is not exaggerated, in fact the opposite case is more plausible. For one, sea level rise is not the same everywhere. Many areas around the world already experience much faster rates of sea level rise than the average global rate shown in Fig 1.  As well, observational data and changing conditions in such places as Greenland suggest if there's a real problem here it's underestimation of future sea level rise. Past IPCC synthesis reports offered rather conservative projections of sea level increase based on assumptions about future behaviour of ice sheets and glaciers, leading to estimates of sea level roughly following a linear upward trend mimicking that of recent decades. In point of fact, observed sea level rise is already above older IPCC projections - and accelerating - while at the same time it appears the mass balance of continental ice once envisioned by the IPCC was overly optimistic (Rahmstorf 2010; Otosaka et al. 2023).

Fast-forward to 2023 and the recent IPCC AR6 Synthesis Report is a bit less nuanced:

Limiting global surface temperature does not prevent continued changes in climate system components that have multi-decadal or longer timescales of response (high confidence). Sea level rise is unavoidable for centuries to millennia due to continuing deep ocean warming and ice sheet melt, and sea levels will remain elevated for thousands of years (high confidence). However, deep, rapid and sustained GHG emissions reductions would limit further sea level rise acceleration and projected long-term sea level rise commitment. Relative to 1995–2014, the likely global mean sea level rise under the SSP1-1.9 GHG emissions scenario is 0.15–0.23 m by 2050 and 0.28–0.55 m by 2100; while for the SSP5-8.5 GHG emissions scenario it is 0.20–0.29 m by 2050 and 0.63–1.01 m by 2100 (medium confidence).

The report goes on to state, however:

The probability of low-likelihood outcomes associated with potentially very large impacts increases with higher global warming levels (high confidence). Due to deep uncertainty linked to ice-sheet processes, global mean sea level rise above the likely range – approaching 2 m by 2100 and in excess of 15 m by 2300 under the very high GHG emissions scenario (SSP5-8.5) (low confidence) – cannot be excluded.

If they cannot exclude such risks - and they know what they are talking about - can you?

Last updated on 20 August 2023 by John Mason. View Archives

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Further viewing

From Peter Hadfield (potholer54 on YouTube) published on Dec 5, 2021

Compare two photos 130 years apart and it looks as though sea levels haven't moved. So why all the fuss about rising sea levels and evacuating islands? This video closes the yawning gap between internet myths and science.


From Peter Sinclair (greenman3610 on YouTube) published on Sep 24, 2009

Denial101x lecture


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Comments 301 to 323 out of 323:

  1. Here is better comparison of satellite and tide guage data from CSIRO.

  2. Despite glacial retreat, shrinking polar ice caps and warming oceans, measured sea level rise is merely incremental.  The eplanations of rising land masses now unburdened by the weight of melted ice, and other theories leave me skeptical.  I would have imagined that Atmospheric Moisture Increase in a warmer atmosphere may possibly account for some of the extra water, but cannot find any documentation of a correlation.  Is AMI  a possible explanation for the merely small levels of sea rise?

  3. Mat @302,

    As Wikipedia shows, the atmosphere contains a tiny portion of our planet's H2O (12,900 cu km) while the oceans contain the vast majority of it (1.338 billion cu km). An increase in global temperature would raise atmospheric H2O by 7% or 9,000 cu km, and with oceans 351 million sq km in size, that would be enough to cause (or prevent) a sea level rise totalling 0.025mm.

    I am not aware of there being a discrepancy between the evaluation of SLR drivers & observed SLR. For instance, IPCC AR5 Chapter 13 Table 13.1 shows the 'residual' to be well inside the confidence intervals.

  4. Matt, see here for discussion of relative contributors to sealevel rise. Melting ice is only one source and contribution easily quantified - convert mass melted from GRACE to volume and spread over area of ocean. It is less important at the moment that steric rise from warming ocean. Isostatic adjustment is neglible and unaware of arguments claiming it to be important.

  5. Hey, I recently came across a paper from 2014, "Global sea level trend during 1993–2012", by Chen (2014). (

    It finds that since 2004, the sea level rise has been decelerating. I have a couple of questions about it since I am not very knowledgeable in this field.

    I think this is the main conclusion of the paper: "GMSL started decelerated rising since 2004 with rising rate 1.8 ± 0.9 mm/yr in 2012."

    However, it does make say the following things in the discussion:

    "Comparison between the GMSL, the global mean steric sea level, and the global mean ocean mass indicates that the decreasing of the rising trend is mainly due to the stalled ocean heat content which started in the early 2000s, when the PDO switched from the warm polarity to cold polarity."

    "Although the stalled upper ocean heat content during the last decade has reduced the rising trend of the GMSL, the global sea level kept rising because of the contribution of the accelerated melting of land ice in the warming climate. This means that if the land ice keeps melting at the same or faster pace due to anthropogenic warming, the world ocean will experience a significant accelerated total sea level rise when the steric sea level transitions to a stage similar to the period during 1993–2003."


    In short, I am not sure what to think of this study. Is the increase in global sea level decelerating? Or is this part of a trend (perhaps the PDO? I don't understand that fully either), and irrelevant if one would look at long-term?


  6. Ossyrial @305,

    You appear to have spotted some of the reasons Chen et al (20140 'Global sea level trend during 1993–2012' have given for their 'deceleration 2004-12' result.  They do also see a significant level of uncertainty in their result although this is not so well handled when presenting their result.

    In a broader context, Visser et al (2015) reviews various methods being used to derive acceleration/deceleration in SLR, methods which do yield contradictory results.

    And the lead author X Chen has published since with Chen et al (2017) 'The increasing rate of global mean sea-level riseduring 1993–2014' which provides a result that supersedes the contradictory result of Chen et al (2014) in that it corrects satellite data and better accounts for other variable factors.

  7. As MA sagely notes, Chen 2014 is dated and newer studies with later data show an acceleration in SLR and with the mass component also increasing.

    Per Yi et al 2017 - Acceleration in the Global Mean Sea Level Rise: 2005–2015:

    "Global mean sea level rise has been accelerating for more than 100 years, and the acceleration in the last two decades seems to further increase"


    "Our results show that the acceleration during the last decade (0.27 ± 0.17 mm/yr2 ) is about 3 times faster than its value during 1993–2014. The acceleration comes from three factors, that is, 0.04 ± 0.01 mm/yr2 (~15%) by land ice melting, 0.12 ± 0.06 mm/yr2 (~44%) by thermal expansion of the seawater, and 0.11 ± 0.02 mm/yr2 (~41%) by declining land water storage."


    "we demonstrate that current advances in satellite gravimetry, and marine in situ measurements enable us to detect the acceleration in global sea level rise from 2005 to 2015, 11 years in total"


    Other studies:

    Cazenave et al 2018 - Global Sea Level Budget 1993–Present

    "Ocean thermal expansion, glaciers, Greenland and Antarctica contribute by 42%, 21%, 15% and 8% to the global mean sea level over the 1993-present. We also study the sea level budget over 2005-present, using GRACE-based ocean mass estimates instead of sum of individual mass components. Results show closure of the sea level budget within 0.3 mm/yr. Substantial uncertainty remains for the land water storage component, as shown in examining individual mass contributions to sea level."

    Cazenave et al 2018 - Contemporary sea level changes from satellite altimetry: What have we learned? What are the new challenges?

    "Most recent studies (e.g., Dieng et al., 2017a, Ablain and Jugier, 2017b, Chen et al., 2017a, Chen et al., 2017b, Nerem et al., 2018b, WCRP, 2018) show that the GMSL is accelerating, and that this acceleration mostly arises from accelerated Greenland and Antarctica ice mass loss."

    SLR Components, p. 1645, Figure 3:

    SLR Components

    Other salient studies:

    1. Dieng et al 2017 - New estimate of the current rate of sea level rise from a sea level budget approach
    2. Ablain and Jugier 2017
    3. Chen et al 2017a - The increasing rate of global mean sea-level rise during 1993–2014
    4. Chen et al 2017b - Groundwater Storage Changes: Present Status from GRACE Observations

    On 2018 sea level rise acceleration:

    "Global sea level rise is not cruising along at a steady 3 mm per year, it's accelerating a little every year, like a driver merging onto a highway, according to a powerful new assessment led by CIRES Fellow Steve Nerem. He and his colleagues harnessed 25 years of satellite data to calculate that the rate is increasing by about 0.08 mm/year every year—which could mean an annual rate of sea level rise of 10 mm/year, or even more, by 2100.

    "This acceleration, driven mainly by accelerated melting in Greenland and Antarctica, has the potential to double the total sea level rise by 2100 as compared to projections that assume a constant rate—to more than 60 cm instead of about 30." said Nerem, who is also a professor of Aerospace Engineering Sciences at the University of Colorado Boulder. "And this is almost certainly a conservative estimate," he added. "Our extrapolation assumes that sea level continues to change in the future as it has over the last 25 years. Given the large changes we are seeing in the ice sheets today, that's not likely."

    Also per Nerem et al 2018:

    "the observed acceleration will more than double the amount of sea-level rise by 2100 compared with the current rate of sea-level rise continuing unchanged. This projection of future sea-level rise is based only on the satellite-observed changes over the last 25 y, assuming that sea level changes similarly in the future. If sea level begins changing more rapidly, for example due to rapid changes in ice sheet dynamics, then this simple extrapolation will likely represent a conservative lower bound on future sea-level change."

    Nerem 2018

  8. Very nice Daniel, thanks for doing that research legwork.

  9. daniel! I have read all the comments and find on the internet something that I can't reconcile.  The Australian Bureau of Meteorology page on

    Pacific Sea Level and Geodetic Monitoring Project

    studies a number of pacific islands from 1993 to 2019. Islands are:Cook Islands; Fiji; Kiribate; Marshall Islands; Nauru; Papua New Guinea; Solomon Islands; Samoa; Tonga; Tuvalu; Vanuatu; Federated States of Micronesia; Niue.

    When I look at the graphs and tables for each island/islands, I find that the g are uniformly even and NOT showing increases in sea level.

    Could you please enlighten me

  10. "When I look at the graphs and tables for each island/islands, I find that the graphs are uniformly even and NOT showing increases in sea level."

    Not sure what your definition of "uniformly even" is.  Did you expect them to be so?

    Firstly, global sea level rise is a global average and the surface of the oceans are anything but level (the surface of the oceans follow the gravitic shape of the Earth and are also subject to solar, lunar, sloshing and siphoning effects and oceanic oscillations, etc, all of which need to be controlled for). 

    From the NCA4, global average sea level has risen by about 7–8 inches since 1900, with almost half (about 3 inches) of that rise occurring since 1993:



    Global SLR

    "Only altimetry measurements between 66°S and 66°N have been processed. An inverted barometer has been applied to the time series. The estimates of sea level rise do not include glacial isostatic adjustment effects on the geoid, which are modeled to be +0.2 to +0.5 mm/year when globally averaged."

    Regional SLR graphics are also available from NOAA STAR NESDIS, here.

    This is a screenshot of NOAA's tide gauge map for the Western Pacific (NOAA color-codes the relative changes in sea levels to make it easier to internalize):

    Western Pacific Tide Gauges

    Clicking on the Funafuti, Tuvalu tide gauge station we see that sea levels are rising by 3.74 mm/yr (above the global average) there, with a time series starting around 1978 and ending about 2011:

    Funafuti - NOAA

    However, the time series used by your BOM link for Funafuti (1993-2019) is shorter and the BOM also does not apply a linear trend line to it like NOAA does:

    Funafuti - BOM

    Feel free to make further comparisons, but comparing a set of graphics with no trend lines vs those with trend lines is no comparison at all.

    From the recent IPCC Special Report 2019 - Ocean and Cryosphere in a Changing Climate - Summary for Policy Makers, September 25, 2019 release (SROCC 2019), the portions on sea level rise:

    Observed Physical Changes
    A3. Global mean sea level (GMSL) is rising, with acceleration in recent decades due to increasing rates of ice loss from the Greenland and Antarctic ice sheets (very high confidence), as well as continued glacier mass loss and ocean thermal expansion. Increases in tropical cyclone winds and rainfall, and increases in extreme waves, combined with relative sea level rise, exacerbate extreme sea level events and coastal hazards (high confidence).

    A3.1 Total GMSL rise for 1902–2015 is 0.16 m (likely range 0.12–0.21 m). The rate of GMSL rise for 2006–2015 of 3.6 mm yr–1 (3.1–4.1 mm yr–1, very likely range), is unprecedented over the last century (high confidence), and about 2.5 times the rate for 1901–1990 of 1.4 mm yr–1 (0.8– 2.0 mm yr–1, very likely range). The sum of ice sheet and glacier contributions over the period 2006–2015 is the dominant source of sea level rise (1.8 mm yr–1, very likely range 1.7–1.9 mm yr–1), exceeding the effect of thermal expansion of ocean water (1.4 mm yr–1, very likely range 1.1–1.7 mm yr–1) (very high confidence). The dominant cause of global mean sea level rise since 1970 is anthropogenic forcing (high confidence).

    A3.2 Sea-level rise has accelerated (extremely likely) due to the combined increased ice loss from the Greenland and Antarctic ice sheets (very high confidence). Mass loss from the Antarctic ice sheet over the period 2007–2016 tripled relative to 1997–2006. For Greenland, mass loss doubled over the same period (likely, medium confidence).

    A3.3 Acceleration of ice flow and retreat in Antarctica, which has the potential to lead to sea-level rise of several metres within a few centuries, is observed in the Amundsen Sea Embayment of West Antarctica and in Wilkes Land, East Antarctica (very high confidence). These changes may be the onset of an irreversible (recovery time scale is hundreds to thousands of years) ice sheet instability. Uncertainty related to the onset of ice sheet instability arises from limited observations, inadequate model representation of ice sheet processes, and limited understanding of the complex interactions between the atmosphere, ocean and the ice sheet.

    A3.4 Sea-level rise is not globally uniform and varies regionally. Regional differences, within ±30% of the global mean sea-level rise, result from land ice loss and variations in ocean warming and circulation. Differences from the global mean can be greater in areas of rapid vertical land movement including from local human activities (e.g. extraction of groundwater). (high confidence)

    A3.5 Extreme wave heights, which contribute to extreme sea level events, coastal erosion and flooding, have increased in the Southern and North Atlantic Oceans by around 1.0 cm yr–1 and 0.8 cm yr–1 over the period 1985–2018 (medium confidence). Sea ice loss in the Arctic has also increased wave heights over the period 1992–2014 (medium confidence).

    A3.6 Anthropogenic climate change has increased observed precipitation (medium confidence), winds (low confidence), and extreme sea level events (high confidence) associated with some tropical cyclones, which has increased intensity of multiple extreme events and associated cascading impacts (high confidence). Anthropogenic climate change may have contributed to a poleward migration of maximum tropical cyclone intensity in the western North Pacific in recent decades related to anthropogenically-forced tropical expansion (low confidence). There is emerging evidence for an increase in annual global proportion of Category 4 or 5 tropical cyclones in recent decades (low confidence).

    B3. Sea level continues to rise at an increasing rate. Extreme sea level events that are historically rare (once per century in the recent past) are projected to occur frequently (at least once per year) at many locations by 2050 in all RCP scenarios, especially in tropical regions (high confidence). The increasing frequency of high water levels can have severe impacts in many locations depending on exposure (high confidence). Sea level rise is projected to continue beyond 2100 in all RCP scenarios. For a high emissions scenario (RCP8.5), projections of global sea level rise by 2100 are greater than in AR5 due to a larger contribution from the Antarctic Ice Sheet (medium confidence). In coming centuries under RCP8.5, sea level rise is projected to exceed rates of several centimetres per year resulting in multi-metre rise (medium confidence), while for RCP2.6 sea level rise is projected to be limited to around 1m in 2300 (low confidence). Extreme sea levels and coastal hazards will be exacerbated by projected increases in tropical cyclone intensity and precipitation (high confidence). Projected changes in waves and tides vary locally in whether they amplify or ameliorate these hazards (medium confidence).

    B3.1 The global mean sea level (GMSL) rise under RCP2.6 is projected to be 0.39 m (0.26–0.53 m, likely range) for the period 2081–2100, and 0.43 m (0.29–0.59 m, likely range) in 2100 with respect to 1986–2005. For RCP8.5, the corresponding GMSL rise is 0.71 m (0.51–0.92 m, likely range) for 2081–2100 and 0.84 m (0.61–1.10 m, likely range) in 2100. Mean sea level rise projections are higher by 0.1 m compared to AR5 under RCP8.5 in 2100, and the likely range extends beyond 1 m in 2100 due to a larger projected ice loss from the Antarctic Ice Sheet (medium confidence). The uncertainty at the end of the century is mainly determined by the ice sheets, especially in Antarctica.

    B3.2 Sea level projections show regional differences around GMSL. Processes not driven by recent climate change, such as local subsidence caused by natural processes and human activities, are important to relative sea level changes at the coast (high confidence). While the relative importance of climate-driven sea level rise is projected to increase over time, local processes need to be considered for projections and impacts of sea level (high confidence).

    Projected Changes and Risks
    B3.3 The rate of global mean sea level rise is projected to reach 15 mm yr–1 (10–20 mm yr–1, likely range) under RCP8.5 in 2100, and to exceed several centimetres per year in the 22nd century. Under RCP2.6, the rate is projected to reach 4 mm yr-1 (2–6 mm yr–1, likely range) in 2100. Model studies indicate multi-meter rise in sea level by 2300 (2.3–5.4 m for RCP8.5 and 0.6–1.07 m under RCP2.6) (low confidence), indicating the importance of reduced emissions for limiting sea level rise. Processes controlling the timing of future ice-shelf loss and the extent of ice sheet instabilities could increase Antarctica’s contribution to sea level rise to values substantially higher than the likely range on century and longer time-scales (low confidence). Considering the consequences of sea level rise that a collapse of parts of the Antarctic Ice Sheet entails, this high impact risk merits attention.

    B3.4 Global mean sea level rise will cause the frequency of extreme sea level events at most locations to increase. Local sea levels that historically occurred once per century (historical centennial events) are projected to occur at least annually at most locations by 2100 under all RCP scenarios (high confidence). Many low-lying megacities and small islands (including SIDS) are projected to experience historical centennial events at least annually by 2050 under RCP2.6, RCP4.5 and RCP8.5. The year when the historical centennial event becomes an annual event in the mid-latitudes occurs soonest in RCP8.5, next in RCP4.5 and latest in RCP2.6. The increasing frequency of high water levels can have severe impacts in many locations depending on the level of exposure (high confidence).

    B3.5 Significant wave heights (the average height from trough to crest of the highest one-third of waves) are projected to increase across the Southern Ocean and tropical eastern Pacific (high confidence) and Baltic Sea (medium confidence) and decrease over the North Atlantic and Mediterranean Sea under RCP8.5 (high confidence). Coastal tidal amplitudes and patterns are projected to change due to sea level rise and coastal adaptation measures (very likely). Projected changes in waves arising from changes in weather patterns, and changes in tides due to sea level rise, can locally enhance or ameliorate coastal hazards (medium confidence).

    B3.6 The average intensity of tropical cyclones, the proportion of Category 4 and 5 tropical cyclones and the associated average precipitation rates are projected to increase for a 2°C global temperature rise above any baseline period (medium confidence). Rising mean sea levels will contribute to higher extreme sea levels associated with tropical cyclones (very high confidence). Coastal hazards will be exacerbated by an increase in the average intensity, magnitude of storm surge and precipitation rates of tropical cyclones. There are greater increases projected under RCP8.5 than under RCP2.6 from around mid-century to 2100 (medium confidence). There is low confidence in changes in the future frequency of tropical cyclones at the global scale.

    C3. Coastal communities face challenging choices in crafting context-specific and integrated responses to sea level rise that balance costs, benefits and trade-offs of available options and that can be adjusted over time (high confidence). All types of options, including protection, accommodation, ecosystem-based adaptation, coastal advance and retreat, wherever possible, can play important roles in such integrated responses (high confidence).

    C3.1. The higher the sea levels rise, the more challenging is coastal protection, mainly due to economic, financial and social barriers rather than due to technical limits (high confidence). In the coming decades, reducing local drivers of exposure and vulnerability such as coastal urbanization and human-induced subsidence constitute effective responses (high confidence). Where space is limited, and the value of exposed assets is high (e.g., in cities), hard protection (e.g., dikes) is likely to be a cost-efficient response option during the 21st century taking into account the specifics of the context (high confidence), but resource-limited areas may not be able to afford such investments. Where space is available, ecosystem-based adaptation can reduce coastal risk and provide multiple other benefits such as carbon storage, improved water quality, biodiversity conservation and livelihood support (medium confidence).

    C3.2 Some coastal accommodation measures, such as early warning systems and flood-proofing of buildings, are often both low cost and highly cost-efficient under current sea levels (high confidence). Under projected sea level rise and increase in coastal hazards some of these measures become less effective unless combined with other measures (high confidence). All types of options, including protection, accommodation, ecosystem-based adaptation, coastal advance and planned relocation, if alternative localities are available, can play important roles in such integrated responses (high confidence). Where the community affected is small, or in the aftermath of a disaster, reducing risk by coastal planned relocations is worth considering if safe alternative localities are available. Such planned relocation can be socially, culturally, financially and politically constrained (very high confidence).

    C3.3 Responses to sea-level rise and associated risk reduction present society with profound governance challenges, resulting from the uncertainty about the magnitude and rate of future sea level rise, vexing trade-offs between societal goals (e.g., safety, conservation, economic development, intra- and inter-generational equity), limited resources, and conflicting interests and values among diverse stakeholders (high confidence). These challenges can be eased using locally appropriate combinations of decision analysis, land-use planning, public participation, diverse knowledge systems and conflict resolution approaches that are adjusted over time as circumstances change (high confidence).

    C3.4 Despite the large uncertainties about the magnitude and rate of post 2050 sea level rise, many coastal decisions with time horizons of decades to over a century are being made now (e.g., critical infrastructure, coastal protection works, city planning) and can be improved by taking relative sea-level rise into account, favouring flexible responses (i.e., those that can be adapted over time) supported by monitoring systems for early warning signals, periodically adjusting decisions (i.e., adaptive decision making), using robust decision-making approaches, expert judgement, scenario-building, and multiple knowledge systems (high confidence). The sea level rise range that needs to be considered for planning and implementing coastal responses depends on the risk tolerance of stakeholders. Stakeholders with higher risk tolerance (e.g., those planning for investments that can be very easily adapted to unforeseen conditions) often prefer to use the likely range of projections, while stakeholders with a lower risk tolerance (e.g., those deciding on critical infrastructure) also consider global and local mean sea level above the upper end of the likely range (globally 1.1 m under RCP8.5 by 2100) and from methods characterised by lower confidence such as from expert elicitation.


    To sum:

    1.  Global sea levels continue to rise, with the rise itself accelerating (due to an acceleration in land-based ice sheet mass losses).  This will continue, for beyond the lifespans of any now alive.

    2.  Beware of the eyecrometer.  It will deceive you, if you allow it to.

    SLR Components

    SLR Components, from Cazenave et al 2018



  11. Jennifer Marohasy has posted a recent blog which claims large sea level falls around Australia over several thousand years.  She appears to be also claiming that sea levels could be falling at the moment.  I would be grateful for any insights the Skeptical Science team can provide about the validity of these arguments. 

    See the post at:

  12. Marohasy conflates local/regional sea levels with global, a fatal error.  

    "She appears to be also claiming that sea levels could be falling at the moment"

    Not without the copious usage of mind-altering substances.  SLR is accelerating as land-based ice sheet mass losses accelerate.

    Read the previous dozen comments.

  13. Dr Marohasy is also conflating modern times (the last 200 years) with the sea level changes of the mid & later Holocene (the last 10,000 years).  She is confusing the picture, by using deceptive rhetoric to suggest (to the casual reader) that the observed global sea level fall of around 1 - 2 meters is part of the overall pattern of sea level fall and is a continuing fall today (despite all those incompetent mainstream scientists providing all that fake evidence of a 20+ cm rise during the past century).

    Despite common sense indicating that current global warming & ice-melt must be causing a rise in mean sea level [as modern tide gauge & satellite measurements do indeed demonstrate] . . . Marohasy is trying to gloss over the reality of modern climate change.

    Her comments are quite bizarre actually ~ this confusion of short- & long-term sea level changes.  Yes, the MSL fell by 1 - 2 meters [ see Clark et al., 2016 ] in the roughly 10,000 years since the peak of the Holocene warm period (as the world continued to cool very slightly) . . . but nowadays the circumstances have produced rapid global warming, with resultant MSL rise.   A rise which Marohasy seems to be trying to conceal with vague & confusing wording.

    The  more interesting question is :- Why  is she undertaking such propaganda-style mendacity?

  14. See also Tamino's demonstration of acceleration in global sea level rise.

  15. Recommended supplemental reading:

    Global data contradict claim of no acceleration in sea level rise, Edited by Scott Johnson, Climate Feedback, Apr 1, 2020

  16. Recommended supplemental reading:

    Rates of global sea level rise have accelerated since 1900, contrary to bloggers’ claims, Edited by Nikki Forrester, Claims Analysis, Climate Feedback, Jan 15, 2021

  17. Peter Hadfield has a new video out on his potholer54 YouTube channel which is now also mentioned in the further viewing section above.

  18. Thank you BaerbelW  ~ and the same Peter Hadfield has brought out a new video on sea level rise, as of a day ago.  This, number 58 in his YouTube climate series.   Title is :- "Are prominent environmentalists buying beachside property?"

    The one you mentioned (number 57) was excellent in debunking the usual strawman myths & faked/false "scientific predictions".

    The new video also humorously looks at sea level and the ongoing Denialist cries about the hypocrisy of very prominent rich Lefties  who are continually buying expensive beach properties which would surely be doomed to inundation in the immediate future.

    Potholer54 provides a handy bunch of rebuttals.  Amusing, too.

    Over 20,000 views already.

  19. Sea level rise is one of the most common topics among the environmental science community and it should be since this topic is a topic that everyone should acknowledge. Sea level rise is caused by global warming which leads to ice and glaciers melting in the polar regions. This caused water to run off to the ocean which causes the sea to be above land.

    This is extremely dangerous, especially to people who live near the shore or anywhere in particular since we cannot predict when there will be flooding. According to the graph above, it is safe to say that the sea level has been rising a lot during the past decades which also shows that global warming is getting worse and worse every single day. For me, sea-level rise is an important topic because it affects human lives in a bad way.

    For example, flooding can cause damage to our areas of living, and it can also harm our drinking water and the crops that we grow for food or the country to send out for trading or any other opportunities. We can help solve this problem by again raising awareness of people living near the shores to watch out for signs of flooding. We can also help each other lower global warming by burning fewer fossil fuels and using more organic stuff. Please help each other resolve this problem for your own safety.

  20. Responding to Fixitsan @84 elsewhere.

    The NTSLF provides tidal gauge data around UK. The UK shows on average 150mm of SLR You say "the tide guages around the UK show some decline in sea level rise. One guage measuring the Thames estuary shows a decline, several Scottish ones too."

    The Sheerness gauge (the gauge in the Thames estury) shows positive SLR.  As for Scotland, Kinlochbervie, Portpatrick & Aberdeen show none of this "decline" you talk of.


    [BL] Note that the post by Fixitsan linked to here has had its contents deleted due to repeated off-topic posts by Fixitsan.

  21. Thank you, MA Rodger.   I had better follow your example, and transfer my reply to Fixitsan into this thread, from his (incorrect) thread "elsewhere".

    To repeat :-

    Curiouser and curiouser, Fixitsan.    While I appreciate your desire to emulate the White Queen in believing six impossible climate things before breakfast ~ I do confess to being intrigued by your statement that "sea level rise is undeniably normal".    Mr Milankovitch and his cycle would suggest (strongly) that the planet is in its natural cooling stage for about the last 4,000 years (minus the last couple of centuries of AGW, of course).

    So why would the sea level be rising recently, without cause?   Or do you define AGW as "normal" ?    (With another five impossible things yet to be enumerated by you.)

  22. Fixitsan,

    Unfortunately, you are completely misinformed on the subject of long term sea level rise.

    Fortunately, Skeptical Science has a post that describes the science and facts of long term sea level rise.  Your claim that sea level has been rising for the psat 20,000 years is simply incorrect. 

    The fact is that sea level increased from about 24,000 years ago until about 4-5,000 years ago.  Then the Earth started cooling (!!!).  The sea level dropped slowly until about 200 years ago.  Then global warming caused the decline to reverrse and sea level rise has been increasing since then. 

    I note that you have provided no linkis to support your wild claims.  Wild, unsupported claims by anonymous internet persons do not haol much weight in scientific discussion.  I look forward to your references that show sea level rise for the past 4,000 years ws increasing.

    I have visited many of the islands described in the linked article at Skeptical Science.  They are low islands formed when coral grew to the surface during the high stand 4,000 years ago.  The decrease in sea level for the past 4,000 years made them islands.  If you insist that sea level has consistently risen for the past 20,000 years, how did coral atolls form?

  23. Please note: the basic version of this rebuttal has been updated on Aug 20, 2023 and now includes an "at a glance“ section at the top. To learn more about these updates and how you can help with evaluating their effectiveness, please check out the accompanying blog post @

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