Since few people are looking up I thought I would update some of my earlier accounts regarding climate change. We’re racing off a cliff! Since 2017 the average global temperature has risen from 0.8°C to 1.1°C in 2021 and it is increasingly unlikely, given division in the U.S. Senate, that any substantive climate change legislation will be enacted. China, India, and Australia also appear committed to the substantial use of coal in the foreseeable future.
The causes of the existential process of climate change can be broadly summarized in the following four charts.
You can access the interactive features of this graph here.
The development of industrialization; and improved farming, shelter, education and public health led to an explosion in the human population growth rate. However, the rate of population increase has been slowing since about 1960 even though the actual population size continues to grow. Most demographers see human population leveling off near 11 billion by the end of this century. For a detailed discussion of future population growth, click here.
However, these demographic projections, though accurate for decades, fail to consider the effects of climate change and the current sixth extinction. Instead, the human population is likely to peak and then begin to decline later in this century for reasons provided by the U.S. CDC.
You can access the interactive features of this graph here.
The growing number of people and their ability to produce more with industrialization powered by petroleum produced an explosion in goods, and later, services. Gross domestic production (GDP) grew both in total dollars and per capita (meaning as people became more affluent on average they bought more things).
You can access the interactive graph here.
Note that:
CO2 emissions from fossil fuels and industry are – in comparison to other greenhouse gases – easier to estimate. Most of our CO2 emissions come from the burning of coal, oil and gas for energy. At the country, regional and global level we have good data or can provide reasonable approximations of the quantity of energy produced, and the sources of this energy. (Hannah Ritchie and Max Roser (2020) – “CO₂ and Greenhouse Gas Emissions”. Published online at OurWorldInData.org. Retrieved from: ‘https://ourworldindata.org/co2-and-other-greenhouse-gas-emissions’ [Online Resource])
However, this graph does not include total GHG emissions because we don’t know about methane and nitrous oxide emissions prior to 1990:
A large share of methane and nitrous oxide emissions come from agriculture, land use and waste. Getting accurate data for all countries, and extending back centuries on the emissions from livestock, soils and different land types is much more difficult. Even if we know how much food is produced from agriculture, and we have standard emissions factors of how much greenhouse gases are emitted per unit of food (for example, per kilogram of rice), this can vary a lot depending on the location, soil type and specific farming practices. We explored this in detail in our article on the differences in the emissions of different food types: depending on the production system, beef in one location can emit more than 10 times as much as beef produced elsewhere. So, unlike CO2 from energy, emissions factors for agriculture and land use can be highly variable. (Hannah Ritchie and Max Roser (2020) – “CO₂ and Greenhouse Gas Emissions”. Published online at OurWorldInData.org. Retrieved from: ‘https://ourworldindata.org/co2-and-other-greenhouse-gas-emissions’ [Online Resource])
Together, global population and GDP increases led to increases in GHG emissions. This growth is exponential, meaning things started slowly and then sharply increased. In this case 1950 was the inflection point, as shown in the first three charts.
You can access the interactive features of this graph here.
The result is an increase in the global average land-sea temperature since the start of record keeping in the 19th century. This fourth graph is not as consistent as the priors because there are short-term climactic changes which ameliorate the greenhouse effect; however, by 1980 short-term differences in climate became overwhelmed by GHG emissions.
How many people the Earth can sustain indefinitely is uncertain, but it depends on how much energy is available and how much people consume per capita. The Earth could sustain fewer people maintaining the current standard of living enjoyed in the developed countries, whereas far more people could be sustained by people living more as they did in the 19th century. Thus we face two existential choices: we can drastically cut our energy demand and rely solely on renewable energy, or we can continue using fossil fuels and risk a severe population crash. Either way, human population will decline over the next 80 to 150 years, but it would be better to manage this decline by people deciding to have fewer children in the age renewables and micro-industrialization.
Developing all the data to produce the graphs, above, took many people and a lot of scientific expertise and administrative skills. However, interpreting these charts is not all that hard. It’s implementing the global policies to change the way people in the developed countries live that are so formidable. We have not yet evolved the capacity, for the most part, to deal with other than our day-to-day wants.
“Extinction is the rule. Survival is the exception.” -Carl Sagan
Which for us? -Stephen Fielding
“It is not clear that intelligence has any long-term survival value.” -Stephen Hawking
Stephen Fielding Images 