Arctic News: Accelerating growth in CO₂ levels in the atmosphere

Saturday, February 25, 2017

Accelerating growth in CO₂ levels in the atmosphere

CO₂ Growth

In 2016, CO₂ levels in the atmosphere grew by 3.36 ppm (parts per million), a new record since 1959 and much higher than the previous record set in 2015.

Worryingly, above graph has a trendline added pointing at a growth rate in CO₂ levels of 6 ppm per year by 2026.

Growth in levels of CO₂ in the atmosphere is accelerating, despite reports that - for the third year in a row - carbon dioxide emissions from fossil fuels and industry (including cement production) had barely grown, as illustrated by the Global Carbon Project image below.

Why is growth in CO₂ levels in the atmosphere accelerating?

So, what makes growth in CO₂ levels in the atmosphere accelerate? As discussed in a previous post, growth in CO₂ levels in the atmosphere is accelerating due to:

Deforestation and Soil Degradation:
Agricultural practices such as depleting groundwater and aquifers, plowing, mono-cultures and cutting and burning of trees to raise livestock can significantly reduce the carbon content of soils, along with soil moisture and nutrients levels.
Climate change and extreme weather events:
The recent jump in global temperature appears to have severely damaged soils and vegetation. Soil carbon loss and enhanced decomposition of vegetation appear to have occurred both because of the temperature rise and the resulting extreme weather events such as heatwaves, drought, dust-storms and wildfires, and storms, hail, lightning, flooding and the associated erosion, turning parts of what was once a huge land sink into sources of CO₂ emissions.
Moreover, extreme weather events can also lead to emissions other than CO₂ emissions, such as soot, nitrous oxide, methane and carbon monoxide, which can in turn cause a rise in the levels of ground-level ozone, thus further weakening vegetation and making plants even more vulnerable to pests and infestations.
Oceans may also be taking up less CO₂ than before:
Oceans have absorbed some 40% of CO₂ emissions since the start of the industrial era. Up until recently, oceans still took up some 26% of carbon dioxide emitted by people annually. As discussed earlier, oceans are getting warmer, and warm water holds less oxygen than cold water. Furthermore, as the water warms, it tends to form a layer at the surface that does not mix well with cooler, nutrient-rich water below, depriving phytoplankton of some of the nutrients needed in order for phytoplankton to grow. Less phytoplankton in the oceans means that oceans become less able to take up carbon dioxide from the atmosphere. A study by Boyce et al. found a decrease of about 1% per year of phytoplankton in oceans globally. Sergei Petrovskii, co-author of a 2015 study, found that a rise in the water temperature of the world’s oceans of about 6°C could stop oxygen production by phytoplankton by disrupting the process of photosynthesis, adding that “About two-thirds of the planet’s total atmospheric oxygen is produced by ocean phytoplankton – and therefore cessation would result in the depletion of atmospheric oxygen on a global scale. This would likely result in the mass mortality of animals and humans.”

Biomass

Sensitivity

Meanwhile, research including a 2014 study by Franks et al. concludes that the IPCC was too low in its estimates for the upcoming temperature rise locked in for current CO₂ levels. A study by Friedrich et al. updates IPCC estimates for sensitivity to CO₂ rise, concluding that temperatures could rise by as much as 7.36°C by 2100 as a result of rising CO₂ levels.

When also taking further elements than CO₂ more fully into account, we could face an even larger temperature rise, i.e. a rise of 10°C (or 18°F) by 2026 (compared to pre-industrial), as further described at the extinction page that specifies the different elements of such a rise, including a 0.5°C rise due to CO₂ emissions from 2016 to 2026. The CO₂ growth discussed in this post appears to be in line with such a rise and in line with the associated loss of carbon sinks and rising vulnerability of carbon pools.

The situation looks particularly threatening in the Arctic where many of the most vulnerable carbon pools are located, where temperatures are rising fastest and where CO₂ levels have recently risen rapidly (see image below with CO₂ readings at Barrow, Alaska).