Context: Impacts – Introduction
Climate Change Impacts – Introduction
- Overview
- Greenhouse Gases
- Temperature Rises
- Other Impacts Context Article Links
- Relevant Background information Sources
1. oVERVIEW
The purpose of this Context article series is to provide a basic context for the climate change impacts on various aspects of the Earth’s major systems related to Weather, Sea and Ice, Land and Food and Forests and Biodiversity. The articles utilise key selected extracts from reputable sources, extracts are copied in italics and parts highlighted in maroon for emphasis.
The aim is to set out in summary, the climate change drivers as well as the effects and impacts on these systems as currently experienced as well as the likely committed changes and possible future consequences, depending on the climate change pathway into the future. This future pathway is itself dependent on the global Greenhouse Gas (GHG) emissions trajectory particularly from Carbon Dioxide (CO2) and Methane (CH4) and whether these continue to increase, level off or are reduced and crucially at what rates/speed.
2. greenhouse gases
A planetary heat balance exists where the heat of the sun reaches the earth surface and a certain amount is reflected back into space in the form of infra red spectra long-waves. The existence of greenhouse gases, primarily Carbon Dioxide but also Methane (CH4) gases in the atmosphere has helped maintain the temperature of the earth much warmer than would otherwise be the case by trapping a certain amount oof this heat naturally over millennia. However this heat balance can be affected by increases or decreases in the amount of GHGs in the atmosphere as well as the reflective effect of icesheets (albedo effect). Climate Change refers to longer term changes in temperature and weather patterns caused by changes in greenhouse gases.
Greenhouse Gas – Human caused Emissions –
Since the start of the industrial age, humans have been steadily increasing the amount of GHGs, principally CO2, into the atmosphere, through the burning of carbon based energy sources, fossil fuels of coal, natural (fossil) gas and petroleum. For most of the past 800,000 years (well before homo sapiens existed) the CO2 concentration in the atmosphere varied between 200 and 280 ppm (parts per million) – 285ppm is taken as the pre-industrial average.
By 1965 total combined GHG concentration, expressed as ‘CO2 equivalent’ where the warming potential of other greenhouse cases are converted to carbon dioxide equivalents had increased to 293, by 1995 they had risen to 365ppm and by 2021 this stood at 472ppm; for CO2 only the figure is 420ppm, or approximately 3,255Gt (Giga tonnes or billion tonnes) of CO2 in the atmosphere. These are concentrations levels not experienced on the planet for millions of years and are approximately 50% above pre-industrial levels and a key milestone in a heating planet. In 2023, total CO2 emissions were 40.6Gt; in 2024 this had increased to 41.6Gt (an increase of x% approximately); fossil fuels contributing 37.4 billion and the rest from deforestation.
3. Temperature Rises
The effect of this increased GHG has been an increase in global annual temperature (the average increase in temperature over the whole planet over a year). Following is a Copernicus table of global surface temperature increases above pre-industrial average (1850-1900)
In 1968 the temperature difference was +0.17 degrees, in 1988 it was +0.46 degrees C and by 2008 it was +0.87 degrees.
In 2023, Global mean temperature was reported by the World Meteorological Organisation as being 1.45 degrees Celsius above the 1850-1900 average . Now the European Union’s Copernicus Climate Change Service has reported (along with a number of other major weather organisations) with ‘virtual certainty’ that 2024 will be the warmest year on record and the first calendar year above 1.5 degrees Celsius.
This has enormous symbolic, legal and climatological significance as the central global climate change agreement; Article 2 of Paris Agreement 2015, commits the world to:
‘Holding the increase in global average temperature to well below 2 degrees Celsius above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 degrees above pre-industrial level [on the basis that this] would significantly reduce the risks and impact of climate change’.
While it requires several years of heating above 1.5 degrees before the climate is officially declared to have exceed this key threshold, the first-year breach is an ominous precursor to this event.
4. Climate Change Impacts – Context Page Links
The following Context articles provide a brief overview of the impacts of the rise in GHGs and temperatures mean for the planet.
Impacts – Forests and Biodiversity
5. Relevant Background information Sources
Global Climate Highlights 2024 | Copernicus
Climate Change: Global Temperature | NOAA Climate.gov
Global Temperature Report for 2023 – Berkeley Earth
MCL – January 2025
(next update schedule: Spring 2028; more regular updates in the ‘Latest News Section’).