Examples of climate change include increases in global surface temperature (global warming), changes in rainfall patterns, and changes in the frequency of extreme weather events. Any human-induced changes in climate will occur against a background of natural climatic variations and of variations in human activity, such as population growth on shores or in arid areas, which increase or decrease climate vulnerability.
Also, the term “anthropogenic forcing” refers to the influence exerted on a habitat or chemical environment by humans, as opposed to a natural process.
“Detection” is the process of demonstrating that climate has changed in some defined statistical sense, without providing a reason for that change. Detection does not imply attribution of the detected change to a particular cause. Attribution of causes of climate change is the process of establishing the most likely causes for the detected change with some defined level of confidence. Detection and attribution may also be applied to observed changes in physical, ecological and social systems.
The instrumental temperature record shows global warming of around 1 °C since the pre-industrial period and a wide variety of temperature proxies together prove that the 20th century was the hottest recorded in the last 2,000 years. Compared to climate variability in the past, current warming is also more globally coherent. The impacts of climate change depend on how much more the Earth warms.
Hottest Days are in 2015 was the hottest year on record, the previous record was broken in 2014, and 2016 is expected to set a new record for the third year in a row. In the past few years’ records have been broken for the longest heatwaves and the bureau of Meteorology has added purple and magenta to the forecast map for temperature up to 54-Degree Celsius.
Rising Sea Levels: Increased ocean temperatures are melting glaciers and ice caps all over the world. Melted ice increases the volume of water in the ocean. Warmer temperature also results in the expansion of the water’s mass, which causes sea levels to rise, threatening low-lying islands and coastal cities.
In 2015, a study by Professor James Hansen of Columbia University and 16 other climate scientists said a sea-level rise of 3 meters could be a reality by the end of the century. Another study by scientists at the Royal Netherlands Meteorological Institute in 2017 using updated projections of Antarctic mass loss and a revised statistical method also concluded that, although it was a low probability, a three-meter rise was possible.
Seas expanding, due to the temperature rise and the melting of ice on Greenland and Antarctica, put at risk hundreds of millions of people in low lying coastal areas in countries such as China, Bangladesh, India, and Vietnam.
Ocean temperature rise
From 1961 to 2003, the global ocean temperature rose by 0.10 °C from the surface to a depth of 700 m. There are variability both year-to-year and over longer time scales, with global ocean heat content observations showing high rates of warming for 1991–2003, but some cooling from 2003 to 2007.
The temperature of the Antarctic’s Southern Ocean rose by 0.17 °C (0.31 °F) between the 1950s and the 1980s, nearly twice the rate for the world’s oceans as a whole. As well as having effects on ecosystems (e.g. by melting sea ice, affecting algae that grow on its underside), warming reduces the ocean’s ability to absorb CO2.
The ocean is warming and acidifying
The Oceans have absorbed most of the extra heat and carbon dioxide (CO2) so far – more than the air – making the sea both warm and more acidic. Warming water is bleaching the coral reefs and driving stronger storms. Rising ocean acidity threatens shellfish, including the tiny crustaceans without which the marine food chain would collapse.
More frequent and intense extreme weather events
Extreme weather events like bushfire, cyclones, droughts, and floods are becoming more frequent and more intense as a result of global warming.
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