climate change

see also:

Introduction

Greenhouse gases and global warming

the facts

the earth is heated by the sun which generally provides 340W/sq.m, of which around 29% is reflected back into space and the rest is absorbed by the atmosphere or earth which becomes warmer and radiates some of this back into space as infrared heat ¹⁾
“greenhouse gases” in clouds and in the upper atmosphere in particular, absorb the infrared rays coming off earth and radiate some of them back to earth acting as a blanket keeping it warm
nitrogen and oxygen, which together account for 99 percent of the atmosphere, has essentially no influence on Earth's temperature because they did not absorb heat, but certain “greenhouse gases” do

carbon dioxide

earth's atmosphere is made up of around 0.04% CO₂ which is thankfully low, as levels above 0.1% will cause humans and other animals to become drowsy
CO₂ is the one of the most important greenhouse gases and is responsible for increasing our average surface temperature from minus 18°C to a livable 14°C
- other greenhouse gases are methane and water vapor (accounts for 36-70% of greenhouse effect)
Natural sources of atmospheric carbon dioxide include volcanic outgassing, the combustion of organic matter, wildfires and the respiration processes of living aerobic organisms.
- in general, the net effect is zero, for example regenerating forests will consume similar amounts of the CO₂ released from wildfires, although this takes decades and may be incomplete if the forests do not flourish
- current volcanic activity releases 130 to 230 megatonnes of carbon dioxide each year
- there is a large natural flux of CO₂ into and out of the biosphere and oceans
- Australia remains an overall carbon sink ²⁾ with a net effect of reducing atmospheric CO₂ levels
Man-made sources of carbon dioxide include the burning of fossil fuels for heating, power generation and transport, as well as some industrial processes such as cement making.
- In 2010, 9.14 gigatonnes of carbon (GtC, equivalent to 33.5 gigatonnes of CO₂ or about 4.3 ppm in Earth's atmosphere) were released from fossil fuels and cement production worldwide, compared to 6.15 GtC in 1990
- once CO₂ is added to the atmosphere, it takes hundreds of years for it to be removed through natural processes
atmospheric concentrations of CO₂ are dramatically rising, especially since 1950
- up until 1800, it was around 250ppm, rising to around 300ppm by 1900 and 315ppm by around 1950 and then has risen sharply to around 370ppm by 2000 and to 415ppm by 2020 - arise of 50%! ³⁾
- it had been mainly below 300ppm for the past 800,000 years ⁴⁾⁵⁾
- each ppm of CO₂ represents around 7.8 gigatonnes CO₂
- a small change in CO₂ can have significant effects on global temperatures

methane

methane is 30x more potent than carbon dioxide as a greenhouse gas but has a much shorter life in the atmosphere
the main sources of methane release into the atmosphere are⁶⁾:
- oil and gas fields
- large diary farms
- some types of landfill
- natural gas leaks from houses

global temperatures are rising

Overall, the global annual temperature has increased at an average rate of 0.07°C (0.13°F) per decade since 1880 and at an average rate of 0.17°C (0.31°F) per decade since 1970, and by 2015 had risen by 1°C since the 19th century ⁷⁾
2023 was the warmest year on record

marine environments

a huge fraction of global flows of carbon and other nutrients pass through marine microbes
- marine microbe populations are partly controlled by deaths due to:
  - viral lysis
  - protistan predation
  - salps (pelagic tunicates)
    - feed by pumping seawater through mucous mesh nets, filtering out and capturing particles such as preferred microbes
    - salps send the carbon in microbes to the deep sea as sinking faecal pellets, or, to predators of salps such as seabirds and sea turtles
    - salps play a major role in controlling the abundances and function of microbial communities in the vast nutrient-poor open ocean, with global implications