Revised 31 October 2022

The role of carbon dioxide (CO2) in the atmosphere and the greenhouse gas effect was known over a century ago by scientists and published by Svante Arrhenius in a peer reviewed international journal as early as 1896. 

Figure 1: 1896 Publication on Climate Change

A few years later, the general public was also aware of the global warming effect of CO2 in the atmosphere due to the burning of fossil fuels. Here is an example of a publication in a New Zealand newspaper, The Rodney & Otamatea Times, published in 1912.

Figure 2: The Rodney & Otamatea Times 1912

A century later, virtually every nation in the world agreed to work together to achieve net zero greenhouse gas emissions by 2050 in the 2015 Paris Agreement. The 2015 Paris Agreement was adopted by a resolution of the United Nations General Assembly. The target of the 2015 Paris Agreement was to hold the global average temperature to well below 2 degrees Celsius above pre-industrial levels and to pursue efforts to limit the temperature increases to 1.5 degrees Celsius. Reductions would be undertaken in accordance with the best science and on the basis of equity. It was recognised that the less-developed nations would require financial assistance from the well-developed nations. The 2015 Paris Agreement recognised that business-as-usual emissions of greenhouse gases must be curbed. Adoption of a carbon budget was agreed upon. The budget is an annual reducing budget, the total size of which is represented by the area under the curve of projected reductions in CO2 emissions.

Figure 3: 2015 Paris Agreement Carbon Budget

Unfortunately, there is a smoke and mirror difference between agreement by world leaders and actual action. Action by our world leaders to mitigate the impact of climate change have been repeatedly delayed until the next meeting. Meeting after meeting has resulted in a lot of hot air. Greta Thunberg has summarised these meetings as being "blah, blah, blah:. The COP26 meeting held in November 2021 was no different. Over the last 50 years there have been over 34 climate conferences, a half dozen major international climate agreements and various scientist’s warnings. Greenhouse gases emissions have continued to accumulate in the atmosphere unabated. Action to match the words have so far been a dismal failure. In 2019, New Zealand declared a Climate Emergency. As of November 2021, there has been so far no sweeping and rapid social change in New Zealand towards mitigating the impact of climate change. New Zealand’s Net Zero Carbon by 2050 policy essentially supports incremental adjustments to business as usual.

As of November 2021, climate warming is 1.2 degrees Celsius above pre-industrial levels (Climate Action TRacker, 2021). In a best case optimistic scenario which assumes full implementation of all announced targets, our climate would be heading towards 1.8 degrees Celsius and as high as 2.4 degrees Celsius above pre-industrial levels by 2100. More commitment is required to keep under 1.5 degrees Celsius. In a real world action scenario based on current policies, our climate would be heading towards 2.7 degrees Celsius and as high as 3.6 degrees Celsius above pre-industrial levels by 2100. This scenario represents a severe existential threat to all life forms on Earth. 

Figure 4: Climate Action Tracker November 2021 Update

A tipping point in our climate system is a threshold which, if exceeded, leads to abrupt and large changes in the state of the system. Some of these changes can be irreversible. Timothy Lenton and colleagues (2008) identified nine tipping points and Will Steffen and colleagues (2015) have identified which tipping elements are most at risk.

Because different climate systems are interconnected, one system can have an impact on another. Each increase in global warming risks a domino like cascade where a series of tipping point thresholds are exceeded. The Greenland ice sheet, Arctic summer sea ice, alpine glaciers, coral reefs, and West Antarctic ice sheets are already undergoing change with a 1.0 degree Celsius increase in global warming above pre-industrial levels. Sea ice reflects more sunlight into outer space than uncovered water where sea ice used to be. With each melting of sea ice, the oceans absorb more heat which increases the level of global warming. The melting of sea ice involves a positive feedback loop where the melting of sea ice results in an acceleration in the melting of more sea ice.

Figure 5: Positive Feedback With Melting of Sea Ice

An existential life-threatening tipping element is the thawing of permafrost. Tundra is located in a large treeless plain in the Arctic regions where the subsoil is frozen.  

This frozen subsoil, or permafrost, holds a vast amount of carbon accumulated from dead plants and animals over thousands of years. 

Figure 6: Tundra in Arctic Region

The atmosphere holds about 589 Petagrams and permafrost stores about 1,700 Petagrams. There is much more carbon locked in permafrost than is currently in the Earth’s atmosphere. There is already evidence of permafrost thawing. Large scale thawing of permafrost would result in irreversible change in climate. The result would be a hothouse Earth where no life forms can survive.

Figure 7: Location of Carbon in the Biosphere

There is a side issue here. Carbon is also stored in the ground in the form of fossil fuels reserves. These reserves include gas (383 - 1,134 Petagrams), oil (173 - 264 Petagrams), and coal (446 - 541 Petagrams). The carbon locked in these fossil fuels far exceed that of carbon in the atmosphere. A year before the 2015 Paris Agreement, Christophe McGlade and Paul Ekins cautioned that most of these fossil fuel reserves must stay in the ground. At the 2015 Paris Agreement, nations agreed to restrict their use of fossil fuels and keep within a carbon budget in order to achieve net zero greenhouse emissions by 2050. But many countries have continued to explore for more reserves of fossil fuels. By doing so, these countries contravene the spirit of the 2015 Paris Agreement and use part of the agreed global carbon budget in exploration for more fossil fuels which should be used to transition from fossil fuels to renewable energy and infrastructure.

In their study of tipping elements at risk, Will Steffen and colleagues (2018) conclude: “Our analysis suggests that the Earth System may be approaching a planetary threshold that could lock in a continuing rapid pathway toward much hotter conditions - Hothouse Earth”.

Figure 8: Hothouse Earth (Steffen et al. 2018)