Country

Tonga

Explore historical and projected climate data, climate data by sector, impacts, key vulnerabilities and what adaptation measures are being taken. Explore the overview for a general context of how climate change is affecting Tonga.

Impacts Sea Level Rise

The systematic warming of the planet is directly causing global mean sea level to rise in two primary ways: (1) mountain glaciers and polar ice sheets are increasingly melting and adding water to the ocean, and (2) the warming of the water in the oceans leads to an expansion and thus increased volume. Global mean sea level has risen approximately 210–240 millimeters (mm) since 1880, with about a third coming in just the last two and a half decades. Currently, the annual rise is approximately 3mm per year. Regional variations exist due to natural variability in regional winds and ocean currents, which can occur over periods of days to months or even decades. But locally other factors can also play an important role, such as uplift (e.g. continued rebound from Ice Age glacier weight) or subsidence of the ground, changes in water tables due to water extraction or other water management, and even due to the effects from local erosion.

Rising sea levels create not only stress on the physical coastline, but also on coastal ecosystems. Saltwater intrusions can be contaminating freshwater aquifers, many of which sustain municipal and agricultural water supplies and natural ecosystems. As global temperatures continue to warm, sea level will keep rising for a long time because there is a substantial lag to reaching an equilibrium. The magnitude of the rise will depend strongly on the rate of future carbon dioxide emissions and future global warming, and the speed might increasingly depend on the rate of glacier and ice sheet melting.

This page supports the exploration of our changing seas through analysis of Historical Sea Surface Temperatures, as well as Historical (satellite measured) Sea Level Anomalies and Future Sea Level Rise Projections (model-based). Use the Dropdown box to select a variable and the toggle underneath the map to change time periods.

Historical Sea Level Anomaly (SLA) is defined as the height of water over the mean sea surface in a given time and region. This dataset contains monthly aggregated global sea surface height products from satellite altimetry observations, provided at a spatial resolution of 0.25ºx 0.25º. Sea level anomalies are computed with respect to a twenty-year mean reference period (1993-2012). Data were produced at CNES as part of the European Space Agency's (ESA) Sea Level Climate Change Initiative (CCI) project and processed by the Climate Resilience Cluster of the European Space Agency’s (ESA) Earth Observation for Sustainable Development (EO4SD) initiative. For more information see here

Projected Sea Level Rise (SLR) indicates future, model-derived relative Sea Surface Hight (SSH). For each of the future scenarios, the dataset is formed by combining 10 geophysical sources of long-term changes in relative SSH. These include 5 ice components (Greenland dynamic ice and surface mass balance, Antarctic dynamic ice and surface mass balance, and glaciers), 3 ocean-related components, all of which are derived from CMIP5 models (dynamic SSH, global thermosteric SSH anomaly, and the inverse barometer effect from the atmosphere), land water storage (also called terrestrial water), and glacial isostatic adjustment (as a change in sea level relative to land). Projected SLR is shown as deviations from the mean value over 1986-2005. Projections are provided for three different RCPs: 2.6, 4.5, 8.5. Data is provided at a spatial resolution of 1ºx1º. Note: the science behind projections of future Sea Level is evolving rapidly, particularly with regard to potential acceleration in polar ice sheet contributions, which could push future Sea Level significantly higher. This product was processed by the Climate Resilience Cluster of the European Space Agency’s (ESA) Earth Observation for Sustainable Development (EO4SD) initiative. For more information see here  

Historical Sea Surface Temperature (STT) data have been generated from satellite observations, derived in near-real time from observations by sensors on meteorological satellites overseen by several agencies globally. This L4 Sea Surface Temperature Analysis data, produced by the ESA Climate Change Initiative (CCI) consists of daily, spatially complete estimated SST data, derived using the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) processing system. The data presented shows monthly average aggregations, provided at a spatial resolution of 0.25ºx 0.25º. This product was processed by the Climate Resilience Cluster of the European Space Agency’s (ESA) Earth Observation for Sustainable Development (EO4SD) initiative. For more information see here

Loading...

Historical Sea Level Anomaly (SLA) is defined as the height of water over the mean sea surface in a given time and region. This dataset contains monthly aggregated global sea surface height products from satellite altimetry observations, provided at a spatial resolution of 0.25ºx 0.25º. Sea level anomalies are computed with respect to a twenty-year mean reference period (1993-2012). Data were produced at CNES as part of the European Space Agency's (ESA) Sea Level Climate Change Initiative (CCI) project and processed by the Climate Resilience Cluster of the European Space Agency’s (ESA) Earth Observation for Sustainable Development (EO4SD) initiative. For more information see here

Projected Sea Level Rise (SLR) indicates future, model-derived relative Sea Surface Hight (SSH). For each of the future scenarios, the dataset is formed by combining 10 geophysical sources of long-term changes in relative SSH. These include 5 ice components (Greenland dynamic ice and surface mass balance, Antarctic dynamic ice and surface mass balance, and glaciers), 3 ocean-related components, all of which are derived from CMIP5 models (dynamic SSH, global thermosteric SSH anomaly, and the inverse barometer effect from the atmosphere), land water storage (also called terrestrial water), and glacial isostatic adjustment (as a change in sea level relative to land). Projected SLR is shown as deviations from the mean value over 1986-2005. Projections are provided for three different RCPs: 2.6, 4.5, 8.5. Data is provided at a spatial resolution of 1ºx1º. Note: the science behind projections of future Sea Level is evolving rapidly, particularly with regard to potential acceleration in polar ice sheet contributions, which could push future Sea Level significantly higher. This product was processed by the Climate Resilience Cluster of the European Space Agency’s (ESA) Earth Observation for Sustainable Development (EO4SD) initiative. For more information see here  

Historical Sea Surface Temperature (STT) data have been generated from satellite observations, derived in near-real time from observations by sensors on meteorological satellites overseen by several agencies globally. This L4 Sea Surface Temperature Analysis data, produced by the ESA Climate Change Initiative (CCI) consists of daily, spatially complete estimated SST data, derived using the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) processing system. The data presented shows monthly average aggregations, provided at a spatial resolution of 0.25ºx 0.25º. This product was processed by the Climate Resilience Cluster of the European Space Agency’s (ESA) Earth Observation for Sustainable Development (EO4SD) initiative. For more information see here

Loading...