Australia: The Land Where Time Began

A biography of the Australian continent 

Climate Change Science – Trends

When the agricultural practices of humans began altering the atmospheric chemistry about 10,000 years ago was the earliest beginnings of global warming. This was exacerbated by the beginnings of the Industrial Revolution as a result of the coal burning which was a cheap energy source. Therefore greenhouse gases have been accumulating in the atmosphere for the past 10,000 years as a result of these factors and the mass production of internal combustion engines. Certain trends that are observable have been taking place and are becoming increasingly obvious, especially over the latter part of the 20th century and continuing into the 21st century. Farmer & Cook have listed the most obvious of the indicators that climate change is already occurring:

Increased atmospheric humidity;

2.      Increased evaporation from water bodies – oceans, fresh water and soils;

3.      Increasing frequency and intensity of  storms and unusual weather patterns;

4.      Glaciers are melting;

5.      Permafrost is melting and releasing methane to the atmosphere;

6.      Decreasing winter snow cover;

7.      Increased temperatures above land and ocean;

8.      Temperature increases in boreholes;

9.      Increasing heat content of the ocean;

10.  Increasing temperatures in the troposphere (lower atmosphere);

11.  Increasing temperature of the upper crust of the solid Earth;

12.  Cooling of the stratosphere;

13.  The movement of plants and animals to higher latitudes and altitudes;

14.  Rising sea level;

15.  Melting of ice sheets, glaciers and sea ice;

16.  Earlier onset of spring and later onset of autumn (fall) each year;

17.  Increasing acidification of the ocean, the ocean waters are becoming more acidic;

18.  Nights are warming more rapidly than days;

19.  Earlier pest infestation outbreaks each year;

20.  Increasing extinction of species of plants and animals.

It is known from temperature records that some places on Earth are becoming hotter while other places are becoming cooler, depending on the season and local factors. A method of calculating this was developed in the 1970s by scientists at NASA’s Goddard Institute of Space Studies (GISS), and by others.

Farmer & Cook have given a number of reasons why the most obvious method, adding all the readings from around the world and dividing by the number of readings, would not reach the correct answer in this case:

  • Most readings would be from the Northern Hemisphere as most of the land and measuring stations are situated there, so the average gained would be biased towards temperatures in the Northern Hemisphere;

  • Some readings would be from different seasons and a particular season may be represented by more readings than another season;

  • Some of the readings would have been taken at night, and others during the day and it is possible that there could be more from one than the other;

  • Some readings would be from old weather stations that are located near vents or surrounded by asphalt or city buildings (the heat island effect), in which case the average temperatures would be increased;

  • Temperature readings from a particular station could be taken more frequently than others.

Methane Clathrates

These are a type of compound structure consisting of a cage formed of molecules that are capable of trapping gases such as methane in a solid form.

A cage composed of water molecules is the most important cage for methane, which is why it is occasionally described as a hydrate. Climatologists and climate change scientists are particularly interested in clathrates because of some key facts about them:

They may comprise a significant proportion of total fossil carbon reserves. Current suggestions are that there may be 500-2,000 gigatonnes (I gigatonne = 1 billion tonnes) of carbon stored as methane clathrates (5-20 % of total estimated reserves). Some estimates put the reserves as high as 10,000 gigatonnes. They are present mainly on the continental shelf where the water is relatively cold; there is enough pressure and enough organic material present to feed the methane-producing bacteria and keep them actively producing methane. Most importantly clathrates can be explosively unstable if there is an increase in temperature or a decrease in pressure, which can happen as a feature of climate change (warming), tectonic uplift or undersea landslides. In shallow Arctic waters methane can already be seen bubbling to the surface in lakes and the ocean in shallow areas of the continental shelf, as well as near disturbed areas such as the Gulf of Mexico, as in the case of the BP oil well blowout in 2010.

Farmer & Cook suggest the danger is imminent that additional methane could be released from the shallow waters of the Arctic in the near future as drilling platforms for oil and natural gas are being sent to the Arctic as this article was being written in June 2012. The real possibility of environmental disaster is suggested by the predictions that significant quantities of oil and natural gas being found off the northern coasts of Alaska, Canada and Siberia as new fields are opened in this pristine but fragile environment around the North Pole.

Temperature – Graphs

Annual global temperatures are shown by plotting on graphs against time. In this way it is possible to show trends in temperature over time and determine visually in which direction the temperature of the Earth is trending.

Temperatures are also shown as anomalies, i.e., temperatures as compared to an average global temperature for a stated time interval (as the average global temperature for the period 1951-1980). It can be easily seen by using this method of referring to temperature that the temperature of the Earth is rising, falling or remaining relatively constant over a given unit of time.

Rising Temperatures – Land and Sea

Temperatures for the land are gathered mostly from weather stations on land throughout the world. The areas with the greatest amount of land and the highest populations are in the Northern Hemisphere. It has been shown by the records that temperatures of both land and sea are rising.

Tropospheric Warming – Stratospheric Cooling

Farmer & Cook suggest the temperatures of the troposphere and the stratosphere are central to the problem of greenhouse warming as it is predicted by the General Circulation Models (GCMs) that as temperature changes because of enhanced greenhouse gas concentrations will have a characteristic profile in these layers, with the mid- and lower troposphere warming and cooling in much of the stratosphere.

Farmer & Cook suggest that If the stratosphere is cooling the Sun could not be responsible of the global warming of the Earth. The atmosphere would be heating throughout, with the stratosphere warming as well if the Sun was causing the warming.

The stratospheric temperature is harder to measure than that of the troposphere where there is a network of measurement stations. Weather balloons, radiosondes, microwave sounding units (MSUs) rocketsondes (a rocket is used to carry the instrument to the stratosphere, LIDAR (light detection and ranging) and satellites have all been used to measure the temperature of the stratosphere.

There are, however, sources of uncertainty with temperature data. It is important to be aware that in spite of the all the attempts to remove uncertainty from the temperature data there are problems that will remain. As Farmer & Cook point out, uncertainty is part of science and good scientists remain sceptical until experiments and tests have been verified; and this is also the case with temperature data.

Whenever data are collected from natural systems for any purpose problems are inherent in the collection. These problems may be due to 1 or more of the following for any natural data set:

  • Missing components or errors in the data;

  • “Noise” in the data that is associated with observations that are biased or incomplete;

  • Random sampling error and biases (non-representativeness) in a sample.

  • Most of this uncertainty is dealt with by the use of statistical methods and other methods.

According to Farmer & Cook the key to an understanding of what constitutes global climate change is first to understand climate and how it operates. It is a complex system involving many variables in time (temporal) and space (spatial) and also there are additional uncertainty sources, such as:

  • Concepts and terminology that are defined ambiguously;

  • Spatial or temporal units that are inappropriate;

  • Inappropriate, or lack of confidence in, underlying assumptions;

  • Uncertainty that result from projections of human behaviour, such as consumption patterns in the future or technological change, which is distinct from uncertainty resulting from “natural” sources, such as climate sensitivity, chaos (the mathematical theory known by that name).

The global climate system is the result of links between the atmosphere, oceans, glaciers, living organisms, the history of the Earth, and the solid Earth (the atmosphere, hydrosphere, cryosphere, biosphere, geosphere). It is possible to understand the cycles of energy in the atmosphere, which is a requirement to investigate the causes and effects of climate change only by considering the climate system in terms of these relationships.

Farmer & Cook suggest it is appropriate to divide the treatment of the system into separate sections, because of the convergence of the individual elements comprising the climate system, and each section deals with a different component.

Sources & Further reading

  1. Farmer, G. Thomas & Cook, John, 2013, Climate Change Science: A modern Synthesis, The Physical Climate Vol.1, Springer Dordrecht


Author: M. H. Monroe
Last updated: 09/12/2014
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