Global Warming And Sea Level Rise Pdf

global warming and sea level rise pdf

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Jump to main content. Contact Us. James G. Titus and Vijay Narayanan.

How is sea level rise related to climate change?

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In this work we present probabilistic projections of ESLs for the present century taking into consideration changes in mean sea level, tides, wind-waves, and storm surges.

Rising ESLs are mostly driven by thermal expansion, followed by contributions from ice mass-loss from glaciers, and ice-sheets in Greenland and Antarctica. Under these scenarios ESL rise would render a large part of the tropics exposed annually to the present-day year event from By the end of this century this applies to most coastlines around the world, implying unprecedented flood risk levels unless timely adaptation measures are taken.

Extreme weather climate extremes contributes to ESL through wind-waves and storm surge. Storm surge is an episodic increase in sea level driven by shoreward wind-driven water circulation and atmospheric pressure 3. Wind-waves are generated when wind energy is transferred to the ocean through surface friction and is transformed into wave energy fluxes 4. When waves reach the coast they interact with the bathymetry and drive an additional increase in water levels through wave set-up 5 and run up 6.

ESLs are exacerbated by tropical cyclones TCs , which significantly intensify wind-waves and storm surge 7 , 8. Recent findings show that global warming will induce changes in storm surges 7 , 9 and wind-waves 10 , 11 , while cyclonic activity may be also affected 8 , These climate extremes, along with sea-level rise SLR will affect ESL and intensify coastal flood risk 1 , 2 , 13 , Global MSL has been rising during the previous and present century 15 with an accelerated rate 16 , 17 , and is projected to keep doing so for the following decades 18 , 19 , Rising MSL can affect the phase and amplitude of tides 21 , 22 , as also shown in historical records Despite these important advances, a coherent global analysis of future ESLs that resolves all the above processes has yet to be conducted.

With a few exceptions 13 , 24 , studies on the intensification of future ESLs and the associated rise in flood hazard or risk have only considered SLR, assuming a stationary climate 1 , 14 and often neglecting wave effects 2 , 25 , 26 as well as TCs 3. Here we combine dynamic simulations of all ESL components during the present century under a moderate-emission-mitigation-policy RCP4. We define ESL as a function of mean sea level rise and water levels driven by tides, waves, and storm surges.

We find that the rise in ESLs will result in unprecedented frequency of catastrophic coastal flooding events along many parts of the world. We provide insights on the relative contributions of the different ESL components and their uncertainties. Present-day values are obtained from a global reanalysis of tides, wind-waves, and storm surges, including simulations of recorded TCs.

All ESL components come as probability density functions PDFs that express the different sources of uncertainty and that are combined through Monte Carlo simulations in order to generate probabilistic projections of ESLs Fig. As a metric to understanding potential impacts we focus on changes in the magnitude and frequency of occurrence of the present year ESL, henceforth ESL Since the study focuses on nearshore ESL dynamics, the global mean values discussed in the manuscript express global coastal averages, omitting the open ocean see also Methods.

Flow diagram showing the procedure to generate the ESL projections. The projected global average ESL and associated uncertainty ranges progressively increase with time and greenhouse gas forcing Fig.

These global average values mask considerable regional variations. For both RCPs a similar spatial pattern of ESL change is projected, with an increasing trend that is consistent along most of the global coastline.

Other areas that under RCP8. The increase in ESLs is weaker along the coasts of the Baltic Sea, where glacial isostatic adjustment results in a relative sea-level fall that counter-balances and in some cases reverses the rise in MSL and climate extremes 5. Present global ESLs, changes in view of climate change and uncertainty. At regional and local scale, however, the magnitude of changes can be relevant.

The geographical regions are highlighted in k. Heavy: median, dotted: 5—95th percentiles very likely and dashed: 17—83th percentiles likely.

Overall there is a tendency for stronger changes toward the end of the century and under RCP8. Local decreases of similar magnitude are projected at scattered locations worldwide. However, for most of the world regional changes in tides are insignificant in comparison to the other ESL components; especially under RCP4.

For the above reasons changes in tides will not be further discussed here, but are provided in the dataset for the convenience of local scale studies. Spatial variations in SLR are considerably lower than the global mean trend, which is positive and accelerates with time Supplementary Fig. The first 2 areas also rank in the top 2 of the highest projected median rise in ESL , as overall SLR prevails over regional changes in climate extremes, under RCP8. Under RCP4. The above regions are projected to experience a decrease in climate extremes under RCP4.

The effects of dynamic sea level and land-water are the weakest among the SLR components, but aggregated for most regions still outweigh changes in climate extremes after the year Break-down of projected ESL contributions and of their uncertainty. Colors represent different components as in the legend and values express the global mean of the median. Also SLR components have unique spatial patterns related to their physical characteristics—those altering ocean mass e.

Glaciers contribute negatively to ESL close to their source, particularly Alaska, but positively elsewhere. Antarctica contributes to ESL negatively at the southern tip of South America but positively everywhere, particularly at low-mid latitudes. Land-water contributions are very small and positive along most coastlines, but negative in the Arabian Sea, as well as parts of the Bay of Bengal and the US west coast Supplementary Fig.

Along West North America the rising contributions from climate extremes outweigh SLR contributions from land-water, Greenland and dynamic sea level, during most of the century, and under both RCPs Figs. In North Europe intensified climate extremes also dominate the effects of glaciers, glacial isostatic adjustment, and dynamic sea level. However, at even smaller scales, changes in climate extremes and tides could gain further importance, dominating most SLR components.

Values shown are expressed in m and reflect spatial averages for 14 regions and worldwide. Wahl et al. We express uncertainty as the very likely range 5—95th percentile and we assess relative contributions from each component to the combined ESL uncertainty see also Methods. To summarize, the upper-tail projections of changes in ESL under a business as usual scenario are mainly driven by Antarctica ice loss Fig.

Contributions are more balanced under a moderate-emission-mitigation-policy scenario with Antarctica surpassing steric effects only by the end of the century Fig. Typically, coastal defenses are targeted to withstand ESLs of a certain intensity related to a frequency of occurrence or return period.

Translating the projected rise in ESLs into the frequency domain shows that under both RCPs already by the present day year event will occur annually in most of the tropics Fig.

Such an intensification in frequency is projected for most coastlines around the world by the end of the century, especially under RCP8. Future frequency of the present day year ESL. Note that the color scale is not linear. Future frequency of the present day year ESL along 14 geographical regions.

The values shown are averages along the global coastline as well as along the coasts of 14 geographical regions. The projected intensification of ESLs will likely push existing structures beyond their design limits 32 , This will drive an increase in coastal risks, which is already projected to rank very high among natural hazards 34 , and has potential to induce massive population movements All the above highlight the challenging nature of coastal adaptation 35 and the need for timely action toward socially fair and effective strategies.

As a result, ESL can be defined as. The procedure to generate the projections consists of the steps summarized as follows see also Fig. Baseline ESL contributions from waves are obtained by a reanalysis, corrected for TC effects based on satellite altimetry data.

Similarly, baseline ESL contributions from storm surges are obtained from another reanalysis, and TC contributions are estimated from a third reanalysis simulating all recorded cyclones.

Future MSLs are available from probabilistic, process-based projections of regional sea-level change. While present tidal elevations are obtained from available datasets, future changes in tides due to SLR are estimated from simulations considering the range of future MSLs.

The period — is considered as baseline for this study. Tidal elevations vary during the tidal cycle and typically the duration of extreme events exceeds that of tidal cycles, therefore high tide will occur at least once during a storm. ESLs typically take place when extreme weather coincides with spring tides 37 , with the latter occurring twice every lunar month.

Waves are simulated using the third generation spectral wave model WW3 4 , 5. Both models have been extensively validated and detailed information can be found in the references provided. Global climate models 39 lack the necessary resolution to fully reproduce the atmospheric fields of TCs, a limitation transferred also to the upper-tail storm surge levels which are usually underestimated by re-analyses such as the present 3. Similarly, we take into account under-predicted TC-driven wave height peaks applying a correction as follows.

The TC tracks data see previous paragraph and the Globwave satellite altimeter dataset 41 are combined to provide maximum H s values for each event along coastal locations. The above approach is sufficient for correcting the amplitude of the H s peaks, which is the information used in the extreme value analysis to follow.

Even though the year return period is discussed in the manuscript, the dataset includes also data for the 5, 10, 20, 50, , , year events. SLR projections. We use a probabilistic, process-based approach to project relative, sea-level rise RSLR up to the end of this century To the first order one can sum individual sea-level components to give total sea-level change that on the regional scale can be written as the sum of each components time dependent global average projection e.

GRE t multiplied by its associated fingerprint e. The contributions in Eq. Each projected global average component is represented by a PDF at each time slice. We randomly sample each PDF times at each time slice and scale each realization by its associated fingerprint. We sum one realization from each component and repeat this for all realizations to give realizations of total projected RSLR at each time slice for each scenario.

Next, we add the time-integrated, scenario independent global field of sea-level change due to GIA 43 multiplied by the relative time difference. We then estimate the combined PDF and calculate quantiles from these realizations at each grid-point to give probabilistic regional sea-level change. The provenance of each sea-level component, its associated fingerprint and time dependent global projection including PDFs are described in Jackson and Jevrejeva For RCP8.

The result of this change is a higher median global sea-level change than the conventional RCP8.

Sea Level Rise Vulnerability Study for the City of Los Angeles

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Many people are interested in climate change and how a changing climate will affect the ocean. With the majority of Americans living in coastal states, rising water levels can have potentially large impacts. Scientists have determined that global sea level has been steadily rising since at a rate of at least 0. Sea level can rise by two different mechanisms with respect to climate change. First, as the oceans warm due to an increasing global temperature, seawater expands—taking up more space in the ocean basin and causing a rise in water level. The second mechanism is the melting of ice over land, which then adds water to the ocean. Home Ocean Facts How is sea level rise related to climate change?

Global probabilistic projections of extreme sea levels show intensification of coastal flood hazard

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Jump to main content. Contact Us. In the last few years, Americans have come to recognize that humanity is changing the earth's atmosphere in ways that we will not be able to reverse over the next century. Some say we should immediately reduce our emissions, while others say we should wait. This web page is devoted to a third, middle view, which is often overlooked: We must prepare now for rising sea level and other consequences of changing climate.

Sea level rise SLR is one of the most severe impacts of climate change, with rising waters threatening to inundate small-island nations and coastal regions by the end of the century. At the same time, SLR is one of the impacts with the largest uncertainties, with different studies projecting widely different ranges over the 21st century. However, a number of studies published in the years since then suggest that the worst-case projections for SLR could be much higher — up to 2m or more this century. In this explainer, Carbon Brief examines estimates of historical sea level rise and the evidence that rates are accelerating.

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