Climate Change Evidence and Causes: Update 2020 (2020) / Chapter Skim
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The Basics of Climate Change
The Basics of Climate Change
Pages 13-30
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From page 13... ...
If all heat energy emitted from the surface passed through the atmosphere directly into space, Earth's average surface temperature would be tens of degrees colder than today. Greenhouse gases in the atmosphere, including water vapour, carbon dioxide, methane, and nitrous oxide, act to make the surface much warmer than this because they absorb and emit heat energy in all directions (including downwards)
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From page 14... ...
Human activities have added greenhouse gases to the atmosphere. The atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased significantly since the Industrial Revolution began.
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From page 15... ...
Ice core records extending back 800,000 years show that during that time, CO2 concentrations remained within the range of 170 to 300 ppm throughout many "ice age" cycles -- see infobox, pg. B4 to learn about the ice ages -- and no concentration above 300 ppm is seen in ice core records until the past 200 years.
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From page 16... ...
Climate records show a warming trend. Estimating global average surface air temperature increase requires careful analysis of millions of measurements from around the world, including from land stations, ships, and satellites.
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From page 17... ...
The heat content of the ocean has increased. Global average sea level has risen by approximately 16 cm (6 inches)
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From page 18... ...
would by itself cause a global average temperature increase of about 1 °C (1.8 °F)
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From page 19... ...
Observed atmospheric temperature changes show a fingerprint much continued Learn more about other human causes of climate change: In addition to emitting greenhouse Earth's surfaces (affecting how much reflecting sunlight back to gases, human activities have also sunlight is sent back into space) and space.
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From page 20... ...
Models project the tempera- Global average surface temperature change ture increase for a business-as-usual 6.0 emissions scenario (in red) and Difference from average aggressive emission reductions, Modelled past warming falling close to zero 50 years from Aggressive emissions reductions temperature (°C)
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From page 21... ...
Day-to-day and year-to-year changes in weather patterns will continue to produce some unusually cold days and nights and winters and summers, even as the climate warms. Climate change means not only changes in globally averaged surface temperature, but also changes in atmospheric circulation, in the size and patterns of natural climate variations, and in local weather.
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From page 22... ...
. In change; ocean factors such as the addition of cool 2013, Arctic summer sea ice extent fresh water from melting ice shelves may also rebounded somewhat, but was still have played a role.
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From page 23... ...
In addition, sea level rise (see Question 14) increases the amount of seawater that is pushed on to shore during coastal storms, which, along with more rainfall produced by the storms, can result in more destructive storm surges and flooding.
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From page 24... ...
Observations show of increased warmth will lead to very significant loss of parts of the Greenland and Antarctic Ice Sheets that the global average sea level and to consequent sea level rise. has risen by about 16 cm (6 inches)
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From page 25... ...
surface ocean (upper box) , and a 380 pCO2 or CO2 concentration decrease in the seawater pH (lower box)
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From page 26... ...
on their present trajectory, without would allow for even less total cumulative emissions since 1875. either technological or regulatory abatement, then the best estimate Based just on the established physics of the amount of heat CO2 absorbs and emits, a doubling of is that global average temperature atmospheric CO2 concentration from preindustrial levels (up to about 560 ppm)
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From page 27... ...
Both theory and direct observations have confirmed that global warming is associated with greater warming over land than oceans, moistening of the atmosphere, shifts in regional precipitation patterns, increases in extreme weather events, ocean acidification, melting glaciers, and rising sea levels (which increases the risk of coastal inundation and storm surge)
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From page 28... ...
that represent the best understanding of the basic laws of physics, chemistry, and biology that govern the Simulating how clouds will change with warming and in turn may affect behaviour of the atmosphere, ocean, land surface, ice, warming remains one of the major challenges for global climate models, and other parts of the climate system, as well as the in part because different cloud types have different impacts on climate, interactions among them. The most comprehensive and the many cloud processes occur on scales smaller than most current climate models, Earth-System Models, are designed models can resolve.
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From page 29... ...
In human systems, for example, infrastructure has typically been built to accommodate the climate variability at the time of construction. Gradual climate changes can cause abrupt changes in the utility of the infrastructure -- such as when rising sea levels suddenly surpass sea walls, or when thawing permafrost causes the sudden collapse of pipelines, buildings, or roads.
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From page 30... ...
If emissions of CO2 stopped altogether, it would take many thousands of years for atmospheric CO2 to return to "pre-industrial" levels due to its very slow transfer to the deep ocean and ultimate burial in ocean sediments. Surface temperatures would stay elevated for at least a thousand years, implying a long-term commitment to a warmer planet due to past and current emissions.
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