Green Living Association

Climate Change Effects on Oceans

<code style=’display: none;’><!–more–></code>&lt;p&gt;Sea levels are rising as the&lt;span&gt; &lt;/span&gt;&lt;a href=”https://www.massaudubon.org/our-conservation-work/climate-change/effects-of-climate-change/on-natural-habitats/ocean-habitats” target=”_self”&gt;oceans warm&lt;/a&gt;, ice melts and water expands. Sea levels have already risen about a foot and could rise several more feet by the end of the century. &lt;/p&gt;&lt;p&gt;Earth’s warming climate is causing sea levels to rise in two different ways. First, warmer air temperatures are causing glaciers and land ice to melt. As the melt water flows into the ocean, the increase in the total amount of water causes the sea level to rise. Second, as ocean water warms, it expands—pushing water farther up along our shores and resulting in &lt;a href=”https://www.massaudubon.org/our-conservation-work/climate-change/effects-of-climate-change/on-natural-habitats/ocean-habitats” target=”_self”&gt;physical changes&lt;/a&gt;&lt;span&gt; &lt;/span&gt;to ocean heat and temperature.&lt;br /&gt;&lt;br /&gt;&lt;strong&gt;Observed Sea Level Rise &lt;/strong&gt;&lt;br /&gt;&lt;br /&gt;Sea level rise is caused primarily by two factors related to global warming: the added water from melting ice sheets and glaciers and the expansion of seawater as it warms. The first graph tracks the change in sea level since 1993 as observed by satellites.&lt;/p&gt;&lt;p&gt;&lt;span&gt;Observations from around the world, including satellite observations, can be used to understand how global warming is affecting temperatures.  Figure 1 shows the global long-term trend, constructed by averaging from all records over the land and sea (sea surface temperatures are measured by ships and, more recently, by satellite).  The temperature has risen by about 1&lt;/span&gt;&lt;sup&gt;o&lt;/sup&gt;&lt;span&gt;C since the start of the record in 1850.  Figure 2 shows the spatial patterns of this warming.  Despite widespread warming throughout the 20&lt;/span&gt;&lt;sup&gt;th&lt;/sup&gt;&lt;span&gt; and 21&lt;/span&gt;&lt;sup&gt;st&lt;/sup&gt;&lt;span&gt; centuries, there is still one area of the world that is unaffected, in the NW Atlantic.&lt;/span&gt;&lt;br /&gt;&lt;br /&gt;&lt;img src=”http://www.greenlivingasc.org/wp-content/uploads/2019/10/Global_Land_surface_temp_0.gif” alt=”” width=”600″ height=”284″ class=”alignnone size-full wp-image-2388″ /&gt;&lt;br /&gt;&lt;br /&gt;&lt;strong&gt;Figure 1:&lt;/strong&gt;&lt;span&gt; Global land and sea surface temperature record from 1850 to 2018. Source: © Climatic Research Unit 2019: &lt;/span&gt;&lt;a href=”http://www.cru.uea.ac.uk/”&gt;http://www.cru.uea.ac.uk&lt;/a&gt;&lt;span&gt; (accessed 5 March 2019). For information on this record see Morice et al. 2012.&lt;/span&gt;&lt;br /&gt;&lt;br /&gt;&lt;img src=”http://www.greenlivingasc.org/wp-content/uploads/2019/10/Global-Rainfall-Pattern.jpg” alt=”” width=”744″ height=”327″ class=”alignnone size-full wp-image-2389″ /&gt;&lt;br /&gt;&lt;strong&gt;Figure 2:&lt;/strong&gt;&lt;span&gt; Distribution of the average temperature change between 1901 and 2012. Source: Australian Academy of Science 2015. Adapted from Figure 2.21 from Hartmann et al. 2013.&lt;/span&gt;&lt;br /&gt;&lt;br /&gt;&lt;strong&gt;Global rainfall patterns&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Rainfall is highly variable in time and in space, and so it is difficult to identify long-term trends in the midst of all the background noise caused by natural variability.  One of the major drivers of rainfall variability at the global scale is ENSO, the El Niño Southern Oscillation.  On average, the world is getting more precipitation (rainfall plus snow) now than it did 100 years ago, although in some regions the trend has been toward decrease. Global trends are shown in Figure 3. &lt;/p&gt;&lt;div class=”media colorbox-cont media-element-container media-image_with_caption” title=”Click to view full size image”&gt;&lt;div id=”file-96″ class=”file file-image file-image-gif”&gt;&lt;div class=”content”&gt;&lt;p class=”fig-image”&gt;&lt;img alt=”Observed precipitation change (rainfall plus snowfall), 1901-2010 and 1951-2010.” height=”406″ width=”912″ class=”media-element file-image-with-caption” src=”https://coastadapt.com.au/sites/default/files/coastadapt_image/T1I2_Figure-3.gif” /&gt;&lt;/p&gt;&lt;div class=”field field-name-field-caption field-type-text field-label-hidden”&gt;&lt;div class=”field-items”&gt;&lt;div class=”field-item even”&gt;&lt;div class=”fig-caption”&gt;&lt;strong&gt;Figure 3:&lt;span&gt; &lt;/span&gt;&lt;/strong&gt;Observed precipitation change (rainfall plus snowfall), 1901-2010 and 1951-2010. Source: IPCC 2013 (Fifth Assessment Report, Working Group 1, Summary for Policy Makers, Figure SPM.2).&lt;/div&gt;&lt;/div&gt;&lt;/div&gt;&lt;/div&gt;&lt;/div&gt;&lt;/div&gt;&lt;/div&gt;&lt;div name=”Extremeevents” data-unique=”Extremeevents”&gt;&lt;/div&gt;&lt;h4&gt;Extreme events&lt;/h4&gt;&lt;p&gt;Working out whether the occurrence of extreme events has changed over time is not straightforward. These events, by definition, occur only rarely, and therefore the sample size for analysis is small making it difficult to (i) identify trends and (ii) (even more difficult) attribute them to global warming. We can say with some confidence that the frequency and duration of heat waves is increasing over some land areas, including Australia.  Heavy rainfall events also seem to be happening more often, and with greater intensity over some land areas. &lt;/p&gt;&lt;h4&gt;Sea-level changes&lt;/h4&gt;&lt;p&gt;One of the outcomes from global warming is sea-level rise, caused by thermal expansion and melting of ice caps and glaciers. Since 1955, something like&lt;span&gt; &lt;/span&gt;&lt;em&gt;90%&lt;/em&gt;&lt;span&gt; &lt;/span&gt;of the excess heat produced by global warming has gone into the oceans, so thermal expansion is an important component of sea-level rise.  Over the period 1901 to 2010, global mean sea level rose by around 0.19 m.&lt;/p&gt;&lt;div class=”media colorbox-cont media-element-container media-image_with_caption” title=”Click to view full size image”&gt;&lt;div id=”file-97″ class=”file file-image file-image-jpeg”&gt;&lt;div class=”content”&gt;&lt;p class=”fig-image”&gt;&lt;img alt=”Global mean sea level relative to the 1900–1905 mean of the longest dataset” height=”366″ width=”654″ class=”media-element file-image-with-caption” src=”https://coastadapt.com.au/sites/default/files/coastadapt_image/T1I2_Figure%204.jpg” /&gt;&lt;/p&gt;&lt;div class=”field field-name-field-caption field-type-text field-label-hidden”&gt;&lt;div class=”field-items”&gt;&lt;div class=”field-item even”&gt;&lt;div class=”fig-caption”&gt;&lt;strong&gt;Figure 4:&lt;span&gt; &lt;/span&gt;&lt;/strong&gt;Global mean sea level relative to the 1900–1905 mean of the longest dataset, and with all datasets aligned to have the same value in 1993, the first year of satellite altimetry data. Coloured lines indicate different data sets. Source: IPCC 2013 (Fifth Assessment Report, Working Group 1, Summary for Policy Makers, Figure SPM.3d).&lt;/div&gt;&lt;/div&gt;&lt;/div&gt;&lt;/div&gt;&lt;/div&gt;&lt;/div&gt;&lt;/div&gt;


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