PART 3: What Are the Consequences of Our Current Policies and Efforts?

Originally published in 2019, updated November 2021

1. What are the consequences of a 2 degree C rise, or more? These seem small amounts; why are they considered serious?

Though they seem to be small compared to the variations we see at different times of the year, these are average temperatures and only small changes can make a difference. Current average temperature rise compared to pre-industrial times is about 1 degree. A 1.5C degree rise is a difficult target which will not disrupt the world environment excessively and one which we could adapt to. Unfortunately, we are on target for much higher rises (at least 2.7 degrees) which would make the world a very difficult place for our grandchildren to live in.

To reiterate, climate outcomes depend on the level of greenhouse gases reached. Scientists have modelled a range of scenarios depending on these levels.

In the scientific world there is a lot of discussion about tipping points.

CLIMATE TIPPING POINTS

The IPCC (International Panel on Climate Change) has defined it as “abrupt and irreversible changes to the climate system”. We have a “budget” of carbon dioxide we can put into the atmosphere before we have serious consequences. We are now over 410 ppm (parts per million) which is equivalent to so many gigatonnes of CO2. Scientists calculate that at certain levels of temperature rise, say above 2 degrees C, there will be major changes to biospheres which will impact on how we live. There will be species extinction, hunger and disease, unliveable heat. It is not going to happen overnight but by 2050 will start to see serious changes.

Modelling these events is difficult but scientists are gaining more certainty in their predictions. For example, we could be heading for a hothouse state where there is little ice; or a wet-house state where temp rises allow more moisture in the atmosphere (1 degree C temp rise = 7% more moisture in the atmosphere); or combinations of both. It will not be the same uniformly around the globe.

We are now causing change 100 times faster than ever recorded.

Let’s look at some possible tipping points:

1. Sea level rise caused by ice loss.

The causes are thermal expansion of oceans (which are absorbing 90% of the extra heat being produced) and melting of land-based ice. Since 1992 when satellite data became accurate the rise has been 3.2mm per year, higher than expected. The rise shown in the graph below shows a possible range of 80 cm to 1 metre by 2100.

Melting of West Antarctic ice would cause a rise of 6 M; East Antarctica 70 M; the Greenland Ice Shelf is degrading and ultimately could cause a 6 M rise. In the Arctic loss of sea ice means less reflection and more absorption of heat into the ocean (although not adding to sea level). All this is happening slowly. It is not abrupt, not this century, but irreversible. It has the potential to cause massive disruption as populations must move.

2. Dieback in the Amazon.

The Amazon is a massive carbon sink, as carbon dioxide is photosynthesised. Deforestation, as is happening (now about 17% gone), when it exceeds 25%, could cause an irreversible change into savannah due to reduced transpiration. We are already seeing droughts and bushfires never seen before, and there are reports that the Amazon has already turned from being a net carbon sink to a net carbon producer.

3. Shutdown of the AMOC (Atlantic Meridonal Overturning Circulation)

This is where warm water in the Gulf stream flows north from the Caribbean up to the North Atlantic, causing cool denser water to flow south. Climate change induced meltwater from Greenland is slowing down this cycle. A 3–4 degrees temp rise could shut it down. Perversely, this could send Northern Europe into a cooling phase (as happened during the Younger Dryas in the 13th Century), but could affect the West African monsoon, El Ninos and the Amazon.

4. Boreal forests of north Russia, Canada, and Europe.

These contain 30% of the world’s forests and warming is happening there twice the speed of the world as a whole. Forest fires would destroy them as they can’t regenerate quickly, causing them to move north and allow grasses and scrub to move into southern areas. Bushfires are already occurring; carbon sequestration is decreasing and at a rise of only 2 degrees there could be abrupt changes.

5. Permafrost.

This is a serious worry. Russia and the Arctic circle hold massive amounts of carbon (peat) from previous temperate periods locked in permafrost. Warming is causing the ice to melt, and this allows the carbon to break down, releasing billions of tons of Methane (which is about 28 times worse that CO2 as a greenhouse gas over 100 years). It has started to happen and by 2100 we could be seeing massive effects.

6. Coral reef die-off

This tipping point is already occurring. We are seeing massive die-off with a 1 degree C rise. At 1.5- 2 degrees warming we can expect to see 90% of coral reefs degraded by 2050. Most of the extra heat cause by a climate change is being absorbed by the oceans. When water warms sufficiently (called marine heatwaves) the coral expels the zooxanthellae and leaves the coral bleached. Combined with nutrient runoff, sediments, and ocean acidification, algae then take over. This not only affects tourism, say on the Great Barrier Reef, but about 500 million people world-wide.

Consequences in Australia and its region:

Please note: With some of the following it cannot be claimed that a particular event, such as a cyclone or a drought or a bushfire, is caused by increases in temperature however it can be said that climate change is setting up the conditions for these events to happen.

  • Increase in frequency and strength of droughts
  • Cyclones more severe
  • More heat waves and extreme weather
  • Worse bushfires
  • Serious depletion and possible death of the Barrier Reef
  • Less snow in the Snowy Mountains and less water in the Murray-Darling Basin for irrigation from surface and groundwater resources
  • Increased sea level of between 0.3 to 1.2 metre by 2100 due to warmer water (thermal expansion), melting glaciers and ice loss. Roughly 1 metre of rise equates to about 100 metres of beach retreat so coastal systems and low-lying areas are at risk
  • Increased ocean acidification. About 26% of CO2 is being absorbed by the oceans and it reacts with the salt making it more acidic. This will affect growth of corals and seafoods such as crustaceans, while warmer water will affect fish farming
  • Social disruption in our region and mass migration of people displaced by rising sea levels, excessive heat, and drought. This is a major concern to security thinkers
  • Species extinction
  • Increase in insurance premiums
  • Massive increase in the cost of adapting infrastructure to cope with all of the above.

Human induced global warming happening very quickly after about 10,000 years of relative stability. Here’s the science behind it and why we should be concerned.