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Beyond Blue Sky 2025 - Chapter 2b

Climate Sensitivity

Quantifying temperature increase in relation to CO2 volume depends on 'climate sensitivity'.  Commonly, this refers to temperature increase resulting from CO2 doubling since the pre-industrial times atmospheric baseline of 280ppm to approx. 550ppm.  The IPCC models predict a range of 2C to 4.5C above 1900, with a best estimate of 3C.  As of June 2024, the world is currently at 427ppm and 1.55C above 1900.

Although both temperature and atmosphere water vapor will continue to increase, specific impacts will depend on geographical location.  For example, higher latitudes together with mid-continental locations are expected to warm sooner and faster.  Also, high rainfall areas should get wetter contrasting drier drought-prone regions.  Much modeling is in progress to predict these regional impacts in greater detail, although we mustn't also forget that it is ultimately God who sends the rains.  The challenge of climate change, particularly dangerous climate change, cannot be understated with magnitude the principal variable.

Evidence for rising temperatures includes:

- Actual reduction in Arctic and Antarctic ice shelves;

- Shrinking of glaciers in the Alps, Greenland, South America, Himalayas etc

- Shrinking snow-cap of Mt. Kilimanjaro

- Rising sea levels as witnessed by Fiji Islands and Bangladesh

Current Trends

The world population, which is now above 8.2 billion (Feb 2025), is expected to reach 9.7 billion in 2050 and 11.2 billion in 2100 assuming a continuing decrease in the average fertility rate from 2.5 in 2015 to 2,25 in 2050 and 2.0 in 2100.  Compounding this, global growth forecasts anticipate that world economic output will double in size by 2050 assuming Business-As-Usual practices.  If this growth continues to be fossil fuel powered global temperatures will increase in parallel during the 21st Century.

Predicting the Future

To address this, the IPCC, in its 5th Asssessment Report (IPCC AR5, 2014) stated that "anthropogenic greenhouse gas emissions are mainly driven by population size, economic activity, lifestyle, energy use, land use patterns, technology and climate policy". They then set out four Representative Concentration Pathways of greenhouse gas emissions and atmospheric concentrations, air pollutant emissions, and land use.  It was worth noting, however, that one pathway, RCP2.6 known as the Stringent Mitigation Scenario, was the only option that aimed to keep global warming below 2C above pre-industrial temperatures (by 2100) since it saw net carbon emissions falling to zero by 2050.  This is required absolutely

Beyond 2100

The temperature will not simply stop rising in 2100.  Since the onset of the Industrial Revolution, a total of 375 GtC has been emitted (with a significant amount being since 2000) while the estimates of the remaining fossil deposits range from 1,500 to 5,000 GtC.  Our remaining 'carbon budget' consistent with a 2C temperature rise is roughly 500 GtC.  We must move to a clean energy future ASAP where the majority of fossil fuels are left in situ as continued use will result in catastrophic temperature increases.

However, Christ will most certainly return before this were to happen.

NEXT Chapter

In this next chapter, I will discuss what "dangerous" climate change means.  We will then return to the Kaya Identity with an initial discussion about economic growth.

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