People have been herding animals and burning or cutting down trees for thousands of years. Before the Industrial Revolution, wood and plants were used for shelter and as building material. Plants also provided food for people and fodder for animals that were herded and that were used for food, ploughing, hunting, herding and transport. Biomass was also burned for heating, preparing food, cooking water, lighting and protection.
Deforestation was the result of people's growing demand for biomass. Deforestation also increased due to trees getting cut down or burned as demand grew for land that could be used for urban purposes, as pasture or to grow more food and fodder.
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The 1850-1900 period that the IPCC uses as base to measure the temperature rise doesn't reflect pre-industrial well, for a number of reasons. Firstly, people's emissions pushed up temperatures long before that. Secondly, the 1850-1900 period was dominated by burning coal to provide heating and energy, which came with sulphur co-emission causing surface cooling, masking the temperature rise.
The rise from 1750 to 2024 in methane, carbon dioxide and nitrous oxide is illustrated by the image on the right, based on IPCC and WMO data.
While emission by people did accelerate since the start of the Industrial Revolution and even more recently, the rise in emission by people had already started thousands of years ago with growth in agriculture, herding of animals and associated deforestation, as illustrated by the combination image below, based on
Ruddiman et al. (2015).
The temperature has risen accordingly since those times. Deforestation and growth in irrigation and numbers of people, livestock and herded animals and their crop waste, sewage and manure resulted in emissions. While much of the forests could initially regrow, the net result was a gradual loss of trees and the cooling aerosols they previously provided and a gradual growth in emissions such as methane, carbon dioxide, carbon monoxide and black carbon (soot).
A
2013 study by Bond et al. calculates that black carbon has a warming effect of about 1.1 W/m², part of which is caused by black carbon darkening the snow and ice cover since pre-industrial times, as discussed on the
aerosols page. By some calculations, the temperature in 1520 had risen by 0.29°C, compared to thousands of years earlier.
September 2025 temperature anomaly
The image below shows how much higher the September 2025 temperature was than it was in 1951-1980.
The above image shows that the September 2025 temperature anomaly was high over both poles and especially high over some areas in Antarctica, where anomalies higher than +10°C versus 1951-1980 were recorded.
As the image below shows, the temperatures recorded over Antarctica throughout September 2025 were higher than in most earlier years, while a record daily high temperature was recorded on October 10, 2025, a +3.62°C anomaly compared to 1979-2000. The inset shows high temperature anomalies versus 1991-2020 at both poles on October 10, 2025.
The image below shows that the global September 2025 temperature anomaly was 1.306°C higher than 1951-1980. Note that the 2025 anomalies were reached under borderline La Niña conditions that suppress temperatures and that the monthly temperature anomaly would be significantly higher when calculated from 1850-1900, which is typically used by the IPCC as baseline.
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| [ Temperature Rise, click on images to enlarge ] |
The full historic temperature rise and the rise to come soon could be much higher, as described on the image and below. The inset is also displayed and discussed in more detail below.
Emissions and Temperature Rise
The observed temperature rise (O) is actually masked by aerosols (M) and the IPCC only includes the rise from the period 1850-1900, ignoring the rise before the period 1850-1900 (P) and the rise that took place to negate the natural fall in temperature. Aerosols could fall out of the air soon, so when adding things up (E1+E2), the historic temperature rise from pre-industrial (O+M+P) is huge.
When also taking into account that the temperature would have fallen naturally (i.e. in the absence of these emissions and in line with Milankovitch cycles, the rise caused by people to negate that could also be included (E3), adding up to an even higher historic temperature rise (O+M+P+H).
Additionally, the full impact of all past emissions may not be fully felt yet, e.g. the full effect of carbon dioxide emissions reaches its peak only a decade after emission (E4). Furthermore, humans are likely to continue to cause emissions in the near future (E5). Finally, additional releases of greenhouse gases are likely to come from what was once called permafrost and from sinks turning into sources, resulting in an additional rise that's already baked into the cake (E6). Therefore, the historic rise plus the rise to come soon (O+M+P+H+F) may approach 5°C.
The diagram below further illustrates the importance of feedbacks and deforestation. Removal of trees has caused deforestation and soil carbon loss since prehistoric times, in turn causing emissions including carbon dioxide, methane and black carbon, while also reducing cooling aerosols released by trees and while also reducing the heat buffer of evaporation that previously cooled the atmosphere. Since prehistoric times, burning wood and deforestation has caused emissions of black carbon and dust that blackened the snow and ice cover, thus speeding up its decline.
The image below illustrates how much the temperature may have risen from pre-industrial times and how much potential there is for a 3°C rise as early as in 2026.
Climate Emergency Declaration
UN secretary-general António Guterres
recently spoke about the need for
“a credible global response plan to get us on track” regarding the international goal of limiting the global temperature rise.
“The science demands action, the law commands it,” Guterres said, in reference to a recent international court of justice ruling.
“The economics compel it and people are calling for it.”
What could be added is that the situation is dire and unacceptably dangerous, and the precautionary principle necessitates rapid, comprehensive and effective action to reduce the damage and to improve the outlook, where needed in combination with a
Climate Emergency Declaration, as described in posts such as
this 2022 post and
this one and as discussed in the
Climate Plan group.
Links
• NASA - Earth by Biome
• Nullschool.net
• Climate-driven chemistry and aerosol feedbacks in CMIP6 Earth system models - by Gillian Thornhill et al. (2021)
• Missing the forest for the trees: The role of forests in Earth’s climate goes far beyond carbon storage - by Sarah Blichner and James Weber (2024)
https://thebulletin.org/2024/05/missing-the-forest-for-the-trees-the-role-of-forests-in-earths-climate-goes-far-beyond-carbon-storage
• Chemistry-albedo feedbacks offset up to a third of forestation’s CO2 removal benefits - by James Weber et al. (2024)
• Aerosols
• Aboveground biomass in Australian tropical forests now a net carbon source - by Hannah Carle et al.
discussed on Facebook at:
• Pre-industrial
• The World lost one third of forests
• The Role of Energy Quality in Shaping Long-Term Energy Intensity in Europe - by Ruta Gentvilaite et al. (2015)
https://www.mdpi.com/1996-1073/8/1/133
• WMO news release: Carbon dioxide levels increase by record amount to new highs in 2024
https://wmo.int/news/media-centre/carbon-dioxide-levels-increase-record-amount-new-highs-2024
WMO Greenhouse Gas Bulletin - No. 21 (issued October 15, 2025)
https://wmo.int/files/greenhouse-gas-bulletin-no-21
discussed on Facebook at:
https://www.facebook.com/groups/arcticnews/permalink/10163357891699679
• Record low Arctic sea ice volume minimum highlights methane danger
• Transforming Society
• Climate Plan
https://arctic-news.blogspot.com/p/climateplan.html
• Climate Emergency Declaration
https://arctic-news.blogspot.com/p/climate-emergency-declaration.html