The last page highlighted increasing temperature over time.
This chapter outlines what happens next.
What’s a couple of degrees?
We’ve known for a while that increasing emissions of greenhouse gases leads to warming.
IPCC Synthesis Reports have told us this with increasing amounts of evidence and certainty in:
1990
1995
2001
2007
2014
For example, in 1990 under the worst case scenario, average global emissions were modelled to lead to 1°C warming above the historical average by 2025 and and 3°C by the end of century.
Scientific understanding has improved over time and our knowledge of how the climate works has become more certain.
The most up to date evidence of this is found in the 2018 IPCC special report on the impacts of warming of 1.5°C. It built on all the reports listed above, and added:
- Human activities are estimated to have already caused around 1.0°C of global warming.
- Warming is likely to reach 1.5°C between 2030 and 2052 if it continues to increase at the current rate.
- Warming caused by humans will persist for centuries to millennia and will continue to cause further long-term changes in the climate system.
1.5 and 2 degrees – what’s the big deal?
A vehicle travelling 35 miles per hour hits an object with twice as much force as one travelling 25 miles per hour, even though the speed has only increased by 40 per cent.
Similarly, the difference between a 1.5 and 2 degree temperature rise seems negligible.
But a little increase leads to disproportionate consequences.
The 1.5°C special report highlights some of the differences in risks between 1.5°C and 2°C, stating:
- Climate-related risks for natural and human systems are higher for global warming of 1.5°C than at present, but lower than at 2°C.
What are some of these risks?
At 2°C, many of these risks increase. Even though it is just 0.5 degrees, in some cases the risks double.
For example:
At 1.5°C warming, about 14 per cent of Earth’s population are projected to be exposed to severe heatwaves at least once every five years, while at 2°C degrees warming, that number jumps to 37 per cent.
But hang on…
Of course floods, droughts, cyclones, bushfires and heatwaves have always been around.
But the key word is risk.
RISK = CONSEQUENCE x LIKELIHOOD
As the globe is allowed to continue to heat, the risk of something happening increases.
It is more likely to happen, and when it does, the consequence will be greater.
We may not see it happen in a single year, and we shouldn’t attribute any one single flood to climate change; but gradually over time, the trend will move from the bottom left to the top right of the risk matrix.
The changes will not be universal. Some areas will suffer more than others for two reasons.
1. They are disproportionately affected by the climatic effects
To date, the impacts of climate change have not been evenly dispersed across the planet and it is projected that they won’t be in the future.
Temperatures are projected increase at different rates, with warming generally higher over land areas than oceans.
Trends currently show that the strongest warming is happening in the Arctic during its cool seasons, and in Earth’s mid-latitude regions during the warm season.
2. Different regions have different capacities to adapt to impacts
A shifting climate may mean that a region receives less rainfall over time, affecting dam levels and water security.
Imagine if this were to happen in a modern city with robust governance. Say, Perth in Western Australia.
Authorities in Perth might manage water availability as dam levels decreased or they might even have the capacity to bring in emergency water with trucks.
If water restrictions affected businesses and the economy, the state could intervene with support.
Over time, it might put in place new water infrastructure, like new pipelines or a desalination plant.
Apply the same scenario to Mogadishu, Somalia and you can begin to see how those ill equipped to deal with climate stressors — for example, because of poor infrastructure or weak governance — can lead to consequences.
A region’s vulnerability is heightened or mitigated by its capacity to adapt.
beyond 2 degrees – what does it mean
At 1.5°C sea level is projected to rise by about 65cm by 2100, the planet will experience some coral reef deaths, it will experience some crop failure and a high risk of species extinction.
At 2°C, the sea rise increases to 80cm, there is widespread coral bleaching and global crop decline.
Beyond 2.0°C, the risks are exacerbated once more and the probability of ecosystem collapses and breaching tipping points increases sharply.
| 1.5°C | 2.0°C | 3 to 4°C |
| Sea level rise by 2100 65cm | Sea level rise by 2100 80cm | Sea level rise by 2100 1m |
| Increased water stress | Glacial retreat reduces water availability in Europe and Americas | |
| Some coral reef mortality | Loss of Indian Ocean coral reefs, widespread bleaching | Gas release from permafrost triples |
| High extinction risk for species | Increased extinction risk | 50% risk of collapse of Atlantic Ocean circulation |
| Some crop failure | Global crop decline | Risk of disintegration of West Antarctic Ice Sheet |
And if you just isolate 1.5°C and 2°C…
| 1.5°C | 2.0°C | Impact of 1.5°C compared to 2.0°C | |
| Loss of plant species | 8% of plants will lose 1/2 of their habitable area | 16% of plants will lose 1/2 of their habitable area | 2x worse |
| Loss of insect species | 6% of plants will lose 1/2 of their habitable area | 18% of plants will lose 1/2 of their habitable area | 3x worse |
| Coral reef decline | 70% to 90% | 99% | Up to 29% worse |
| Extreme heat | 15% of the global population exposed to severe heat every 1 in 5 years | 37% of the global population exposed to severe heat every 1 in 5 years | 2.6x worse |
| Ice free Arctic summers | At least once every 100 years | At least once every 10 years | 10x worse |
But it’s not about that.
It’s not about the sea rising to your knees. It’s not about the extra 40°C day here and there.
It’s not about the 1 in 100 year flooding event that occurs, and occurs again.
Everything is interconnected
This is perhaps one of the most misunderstood parts of the climate equation.
A small increase in temperature isn’t just a small increase in temperature. It’s a pressure point.
Think about a drought.
Yes, it doesn’t rain for a bit. This probably means crop damage, less water availability, more soil erosion and increase fire risk.
But scratch the surface and it also means an increased cost of food, job losses and reduced incomes.
And with those job losses and reduced incomes may lead to crime, health impacts, domestic violence…
And on it goes.
what are we on track for?
The IPCCs Representative Concentration Pathways assess different futures under selected climate scenarios. Using modelling, they equate greenhouse gas emission output with an end of century global temperature increase.
While these pathways produce a variety of outcomes, we can assess with a fair degree of certainty that warming will not continue in perpetuity.
The IPCC 1.5 degree report says warming is likely to reach 1.5°C between 2030 and 2052 if it continues to increase at the current rate. From there, it may continue on to beyond, perhaps even well beyond 2°C, by the end of the century.
Others say that if you factor in country policies around the world, the warming may be closer to 3°C by the end of the century, with pledges taking it closer to 2°C at best.
| Update November 2021 In the lead-up to COP26, a number of countries announced new pledges and targets. The IEA has released new analysis stating that if these pledges were implemented, warming could remain at 1.8°C by the end of the century. The Climate Action Tracker has also released analysis stating pledges, if implemented, would limit warming to 1.7°C to 2.1°C. |
But this relies on a crucial aspect — it’s one thing to set a target 🎯 but it doesn’t count for much if you aren’t able to implement it or you’re not on track to meet it.
A handful countries are on track.
Others are heading in the right direction, but need to do more, fast.
And for some, it’s really hard to see how they will achieve what they’ve pledged.
So the conclusion one can draw, is that the world is on track for a temperature closer to 3°C and everything that it entails, including around 1 metre of sea level rise, reduced water availability from glacial retreat, and the risk of breaching ecological tipping points.
Amongst the hype and the denial and the chaos, you’ll be hard pressed to find an expert in the field who disagrees.
This is the seriousness of the matter and reality we face.
There is still time to course-correct, but it’s grim, and young people are justified in being concerned about a temperature that will continue to rise.
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Further reading:
NASA, A Degree of Concern: Why Global Temperatures Matter
Carbon Brief, Do COP26 promises keep global warming below 2C?