The Most Important Insights from the IPCC 1.5 °C Report
- October 10, 2018
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IPCC reports tend to be long and boring. Here is the short and interesting version of the latest report:
1.5 °C emissions pathways are truly daunting
It is difficult to see any realistic way in which we will achieve the 1.5 °C emissions reduction pathways illustrated below. Immediate and sharp reductions are needed, but even full adherence to all national Paris agreement commitments will result in annual emissions by 2030 that are double the requirement for achieving 1.5 °C.
Large negative emissions will be required
As clearly illustrated in the figure above, most scenarios achieve net-zero emissions around 2050 and net-negative emissions afterwards. The illustrative scenarios (P1-P4) in the above figure are given below, showing that only P1 can achieve this outcome without bioenergy with CO2 capture and storage (BECCS). This scenario relies heavily on massive reductions in global energy consumption: 26% below today's levels by 2030. Given the growth demands of 6 billion (and counting) developing world citizens, we will do well to keep global energy consumption from increasing 26% by 2030.
1.5 °C instead of 2 °C is important
As illustrated below, the five main reasons for concern increase significantly from 1.5 to 2 °C. Unique and threatened ecosystems (e.g. coral reefs, glaciers and the Arctic region) will be most severely affected by a further increase to 2 °C. The one that I'm most concerned about is the "distribution of impacts" risk rising from moderate to high. This essentially means that those billions of people least responsible for climate change will be at high risk of facing its worst impacts. The risk of large-scale singular events (e.g. massive sea level rise due to disintegration of the Greenland and Antarctic ice sheets) also becomes uncomfortably high at 2 °C.
Significant increase in available carbon budget
Even though the climate change community does not like to admit it, it has been clear for several years that climate models have been overpredicting global warming. The new IPCC report finally moderates climate models with actual observations and thereby calculates significant increases in carbon budgets. In essence, the budget that was previously linked to a 2 °C rise will now only lead to a 1.6 °C rise. 1.5 °C may well be practically impossible, but the sizable boost in carbon budget means that 2 °C now becomes a more realistic possibility.
Synergies with sustainable development goals
The report is confident that the 1.5 °C scenario has much greater synergies than trade-offs with other sustainable development goals. It is clearly acknowledged that low energy demand (e.g. the P1 scenario discussed above) and low general consumption are critical for increasing synergies and limiting trade-offs. This is something I wholeheartedly agree with, but I think the rate of consumer demand reduction assumed in preparing the figure below is unfortunately completely unrealistic.
Aim for the stars and maybe reach the moon
In general, my impression of the IPCC 1.5 °C report is that it was written to encourage the world to try and reach 1.5 °C and, in so doing, maybe achieve 2 °C. Even though I think that 1.5 °C is essentially impossible, the significantly increased carbon budget means that 2 °C could be achieved if enough people commit to the 1.5 °C ideal. I sincerely hope that this report will contribute significantly to the growing sense of climate urgency around the world.