This blog is expressly directed to readers who do not have strong training or backgrounds in science, with the intent of helping them grasp the underpinnings of this important issue. I'm going to present an ongoing series of posts that will develop various aspects of the science of global warming, its causes and possible methods for minimizing its advance and overcoming at least partially its detrimental effects.
Each post will begin with a capsule summary. It will then proceed with captioned sections to amplify and justify the statements and conclusions of the summary. I'll present images and tables where helpful to develop a point, since "a picture is worth a thousand words".
Tuesday, August 29, 2017
Tuesday, August 15, 2017
A draft of the Fourth National Climate Assessment reports that the global average temperature for the 30-year period from 1986 to 2016 rose by 1.2°F (0.7°C). It is extremely likely that activities by humans have been the principal cause of this warming. Extreme temperature and rainfall events have increased over this time, as have forest wildfires.
global map grid of historical changes in the average temperature for the period
1986-2016 relative to the average from the six-decade reference period 1901-1960,
in °F. No data are available at the
poles, indicated by gray.
Source: CSSR; https://www.nytimes.com/interactive/2017/08/07/climate/document-Draft-of-the-Climate-Science-Special-Report.html.
Extreme climate-related weather events have increased in number and severity. Since 1980 the cost of such calamities in the U. S. is over US$1 trillion. Extreme events can impact water quality, agriculture, human health, infrastructure, and lead to disaster events. In the U. S. the number of high temperature records in the past 20 years is much higher than the number of low temperature records (very high confidence).
The waters of the oceans have absorbed about 93% of the heat accumulating in the Earth system due to global warming since the 1950s (very high confidence). This affects climate patterns around the world.
In the Arctic, ice sheets overlaying land have been melting for at least the last three decades; in some locations the rate of loss is accelerating (very high confidence). The rate of melting of ice sheets over Greenland has accelerated in the last few years (high confidence). As this ice melts the water flows to the ocean, resulting in a net increase of sea level.
Arctic sea ice has been imaged since satellite flights permitted. The sea ice floats on the Arctic Ocean; its area expands and contracts in freeze-thaw seasonal cycles without any net change to global sea levels. Rather, the extent responds to changes in air and sea temperatures. The least extent, i.e., the most melting, occurs typically in September. Striking images showing the loss of September sea ice from 1984 to 2016, both in thickness (color coded white as having been formed at least four years earlier) and in overall surface area, are shown in the images below:
Satellite images of Arctic sea ice extent and thickness in September, for 1984 (top) and 2016 (bottom). The color bar shows the local age of the ice in years, a proxy for its thickness, from recent (dark gray) to more than 4 years (white).
Source: Adapted from CSSR; https://www.nytimes.com/interactive/2017/08/07/climate/document-Draft-of-the-Climate-Science-Special-Report.html.
Ocean waters are absorbing more than 25% of the carbon dioxide emitted into the atmosphere by burning fossil fuels. Carbon dioxide is weakly acidic when dissolved in water, increasing its acidity (very high confidence). This negatively impacts marine ecosystems in many important ways.
Heavy precipitation events are projected to continue increasing over the 21st century (high confidence). In the western U. S., large reductions in mountain snowpack, and more precipitation falling as rain rather than snow, are projected as the climate warms (high confidence). These trends are attributed to human activity (high confidence). They will likely worsen considerably as the climate warms (very high confidence). In the absence of reductions in emission rates long-duration hydrological drought, due to decreased retention of soil moisture, becomes more likely by the end of the century (very high confidence).
New carbon dioxide released “today” is long-lived, persisting in the atmosphere for decades to thousands of years. Therefore it’s important to note that the relationship between total atmospheric CO2 concentration and the increase in global temperature is a linear one.
We must all undertake to reduce emissions of GHGs in our personal lives, and support policies promoting reductions at the state, national and international levels.
Tuesday, August 1, 2017
Summary. Scientific research is pursued as an unbiased, objective inquiry into the properties of the natural world. The foundations of climate science were laid over the last two hundred years, establishing that man-made production of carbon dioxide induces an atmospheric greenhouse effect. Current political influence seeks wrongly to raise doubts about these immutable facts.
He considered that de Saussure’s heliothermometer provided an analogy for the Earth. As described by Dufresne (cited above), Fourier first noted that the heat accumulated within the box is not dissipated by circulation to its exterior, and second, that the heat arriving from the sun as (visible) light differs from what he calls “hidden (i.e. invisible) light”. Rays from the sun penetrate the glass covers of the box and reach its bottom. They heat the air and walls that contain it. These rays are no longer “luminous” (i.e. are not visible) and preserve only properties of “dark” (or invisible) heat rays. Heat rays do not freely pass through the glass covers of the box, or through its walls. Rather, heat accumulates within it. The temperature in the box increases until a point of thermal balance is reached such that the heat added from the sun is balanced by the poor dissipation of heat through the walls.
Heat radiation had been discovered earlier during Fourier’s lifetime and he probably was familiar with this phenomenon. Today we identify heat as infrared radiation, and de Saussure’s heliothermometer as a fine example of a greenhouse. Indeed any car standing closed in the sun becomes a greenhouse. When we get in it we are immediately immersed in a very hot atmosphere.
John Tyndall showed that carbon dioxide absorbs heat radiation. Tyndall was a British physicist whose research centered around radiation and energy. He became a fellow of the Royal Society in 1852, and became a professor at the Royal Institution of Great Britain.
Tyndall’s differential spectrometer for measuring radiant heat absorption by a gas. The gas was introduced into the long tube in the upper center. Loss due to absorption of radiant heat by the gas was compared to a reference heat signal produced at the left. The losses were compared in the double-conical thermopile at left center, and the resulting electrical signal was measured by the galvanometer (a sensitive measuring device) at the lower center.
© 2017 Henry Auer