Since the industrial revolution, the air temperature has risen 0.9°C on average. This has already caused melting of the polar ice caps, a 20cm rise in sea level, record high temperatures, bleaching of coral reefs and record frequency of severe droughts and floods. (1)

By studying ice core samples, scientists have been able to measure the historic levels of atmospheric gases over the past 800,000 years. The studies clearly show a pattern of low CO2 levels (180ppm) during an ice age (cool oceans absorb more CO2) and high CO2 levels (300ppm) during the peak of an interglacial period. These cycles take around 100,000 years to complete and are related to the procession of the earth’s orbit around the sun, affecting the amount of solar radiation reaching the earth. (2) (3) (4)

Since the industrial revolution, CO2 levels in the atmosphere have risen from 280ppm to 410ppm. A rate of change faster than any event seen in the entire geological record.

When the sun emits UV radiation, part of that radiation is absorbed by the ozone layer, however most of the sun’s radiation reaches the earth’s surface and is reflected back into space as infrared radiation. Greenhouse gases trap some of that infrared radiation by reflecting it back to earth. Greenhouse gases make up 0.43% of the atmosphere and include CO2, methane and nitrous oxide. CO2 makes up around 80% of the greenhouse gases. (5)

Water vapour also acts as a greenhouse gas, however there is a limit to its heating effect because it condenses into clouds and falls back to earth as precipitation. CO2 is a non-condensable gas, meaning it stays in the atmosphere for much longer periods of time and has a long-lasting effect on the temperature of the atmosphere. (6)

Scientists have been able to measure the global output of CO2 and directly correlate those findings with the rise in atmospheric temperature over time. (7)

Humans have emitted over 580 billion metric tonnes of CO2 into the atmosphere since the start of the industrial revolution. Of that amount, approximately 26% was absorbed by the oceans, 30% was absorbed by forests and 44% was retained in the atmosphere. (8) (9)

The major sources of global CO2 emissions are:

Electricity production 25%

This includes fossil fuels burned for the production of electricity used to power and heat people’s homes and businesses.

Agriculture, forestry and other land use 24%

This is the CO2 produced by intensive agriculture, deforestation, and other land use practices.

Industry 21%

This includes CO2 emitted by onsite burning of fuels at industrial sites.

Transportation 14%

This includes fossil fuels burned by cars, buses, trains, planes, ships and other forms of transport.

Fuel refinement and processing 10%

This is the CO2 released by the process of mining, refining and transporting fossil fuels.

Heating and cooking 6%

This includes the CO2 emitted through the direct burning of carbon-based fuels to heat buildings and cook food.

For the past 30 years, scientists have been collecting large amounts of data on the climate and have been able to create models to predict the effect of climate change in the future.

The most recent findings were published in October 2018 by the Intergovernmental Panel on Climate Change (IPCC) in a special report titled, “Global Warming of 1.5°C”.

The report looks at the findings of over 6000 peer-reviewed scientific studies and makes predictions of what we can expect in the future, based on a range of Greenhouse Gas emission scenarios.

The report estimates that the best-case scenario is a warming of about 1.5°C if we cut all sources of greenhouse gas emissions by 2050. (10)

A rise in air temperature of 1.5°C would kill most the coral reefs; increase sea levels to 0.5m above pre-industrial levels by 2100 and continued rising into the future; cause temperature extremes for much of the tropics; increase rainfall in some areas; while causing extended droughts periods in other areas.

According to the IPCC report, if we cut all greenhouse gas emissions by 2100, the best-case scenario is a temperature rise of 2°C. This would cause the polar ice caps to melt, flood vast areas of farm land, displace almost 1 billion people and create temperature extremes that would make some parts of the world uninhabitable.

These best-case scenarios don’t take into account feedback loops that could greatly increase the rate and impact of climate change.

One concern is the billions of tonnes of methane trapped beneath the arctic icecaps and in permafrost. The melting of these areas has already released vast quantities of methane into the atmosphere above the arctic circle. As they release more methane, the temperature rises further, increasing the thawing and therefore releasing even more methane. Methane eventually breaks down into CO2 and water, however over a 100 year time period, it is 25 times more powerful as a greenhouse gas than CO2. (11) (12)

Another feedback loop is the release of CO2 from the oceans as they continue to warm. The Ocean is a huge carbon sink, soaking up 12 million tonnes of carbon dioxide a day. In the last 100 years, the oceans have absorbed so much CO2 that their pH has dropped from 8.2 to 8.1, which is a 26% increase in acidity. That is the highest rate of change of oceanic pH in the last 50 million years. As the ocean warms, the amount of CO2 that it can absorb decreases. This could lead to a positive feedback loop where warmer temperatures release more CO2 from the oceans, in turn increasing the temperature. (13)

The IPCC report shows that if we continue to pollute at the current rate until 2100, we can expect a temperature rise of 4-5°C. That would devastate much of the human population and create a mass extinction event because very few lifeforms would have time to adapt.

The scientists have been warning about the effects of climate change for decades. We are now past the tipping point and need to act fast to prevent a future catastrophe.

The recommendations from the IPCC report include switching all energy to solar, wind and battery power, making all cars electric, protecting all remaining forests, reforesting degraded lands, reducing our consumption of beef and using 100% sustainable agricultural practices.

Even if we take all these steps by 2050, we’re still facing a 1.5°C temperature rise and all the consequences that go with it.

Ecological systems must be factored into the economy, otherwise the systems that sustain life on earth will collapse. In order to maintain a balance in the ecosystem, we as humans need to reduce our population to a sustainable level and stop basing our economic success on infinite growth.

The cost of solar and wind power is decreasing exponentially and is already cheaper than coal powered electricity. The transition to renewable energy is picking up pace and we may just have a chance to prevent the most catastrophic effects of climate change if we act now.

References

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2. Petit J.R., Jouzel J., Raynaud D., Barkov N.I., Barnola J.M., et al. 1999, Climate and Atmospheric History of the Past 420,000 years from the Vostok Ice Core, Antarctica, Nature 399: 429-436.
3. Lüthi, D., M. Le Floch, B. Bereiter, T. Blunier, J.-M. Barnola, et al. 2008. High-resolution carbon dioxide concentration record 650,000-800,000 years before present. Nature 453: 379-382. doi:10.1038/nature06949.
4. EPICA Community Members, 2004. Eight glacial cycles from an Antarctic ice core. Nature 429: 623-628.
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10. IPCC (2018) Global Warming of 1.5°C. A Special Report by the Intergovernmental Panel on Climate Change. October 2018.
11. Knoblauch C, Beer C, Liebner S, Grigoriev M N, Pfeiffer E-M (2018): Methane production as key to the greenhouse gas budget of thawing permafrost; Nature Climate Change, DOI: 10.1038/s41558-018-0095-z
12. Yvon-Durocher G., Allen A. P., Bastviken D., Conrad R., Gudasz C., St-Pierre A., Thanh-Duc N., del Giorgio P. A. (2014) Methane fluxes show consistent temperature dependence across microbial to ecosystem scales. Nature, 2014; 507 (7493)
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