DEFORESTATION AND OTHER LAND-USE CHANGES, IN PARTICULAR WILDFIRES

During the decade from 2006 to 2015, emissions from deforestation and other land-use change added another 1.0±0.5 GtC (3.3±1.8 GtCO₂) on average, on top of the above emissions from fossil fuel and cement. In 2015, according to the Global Carbon Project, deforestation and other changes in land use added another 1.3 GtC (or 4.8 billion tonnes of CO₂), on top of the 36.3 billion tonnes of CO₂ emitted from fossil fuels and industry. This rise in emissions from deforestation and other changes in land use constitutes a significant increase (by 42%) over the average emissions of the previous decade, and this jump was largely caused by an increase in wildfires over the past few years.

In 2016, monthly mean global CO₂ levels didn't get below 400 ppm. It was the first time that this happened in over 800,000 years.

On their way up, global CO₂ levels fluctuate with the seasons, typically reaching an annual minimum in August. In August 2016, CO₂ levels reached a low of 400.44 ppm, i.e. well above 400 ppm. In September 2016, carbon dioxide levels had gone up again, to 400.72 ppm. Importantly, a trend is contained in the data pointing at a CO₂ level of 445 ppm by the year 2030.

SENSITIVITY

Meanwhile, 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 taking other elements than CO₂ more fully into account, the situation looks to be even worse than this, i.e. the global temperature rise could be as much as 10°C (or 18°F) over the coming decade, as further described at the extinction page, at: http://arctic-news.blogspot.com/p/extinction.html

LAND SINK

There has been an increase of the land sink over the years, which a recent study attributes to higher CO₂ levels in the atmosphere. While this increase of the land sink appears to have held back a stronger temperature rise for some time, there are indications that this land sink is now decreasing.

Why is the land sink now decreasing?
- 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.
- The recent jump in global temperature appears to have severely damaged soils and vegetation through extreme weather events such as hailstorms, lightning, flooding, heatwaves, drought, dust-storms and wildfires, and the associated erosion, turning parts of what was once a huge land sink into sources of carbon dioxide emissions. Even worse, such extreme weather events can also lead to further emissions, including soot, nitrous oxide, methane and carbon monoxide, which can in turn cause increases of ground-level ozone that further weakens vegetation and makes plants vulnerable to pests and infestations.
- As a 2009 study warned, higher temperatures could also cause decreased canopy transpiration, due to less widely opened plant stomata and the resultant increase in stomatal resistance at higher atmospheric carbon dioxide concentrations. As a result, low cloud cover is decreasing over most of the land surface, reducing planetary albedo and causing more solar radiation to reach the surface, thus further raising temperatures beyond the level of viability for many species.

CONCLUSION

In conclusion, while CO₂ emissions from fossil fuels and industry may have barely grown, levels of greenhouse gases are steadily increasing, if not accelerating. At the same time, extreme weather events are on the rise and there are further factors contributing to cause the land carbon sink to shrink in size. Furthermore, the IPCC appears to have underestimated sensitivity to CO₂ rise. As a result, temperatures cannot be expected to come down from their currently very high levels.

GLOBAL SEA ICE

As another reflection of an increasingly warmer world, the combined extent of Arctic and Antarctic sea ice is currently at a record low. On November 12, 2016, combined global sea ice extent was only 23.508 million km².

Some of the results of the dramatic global sea ice decline are:
- Huge amounts of sunlight that were previously reflected back into space are now instead absorbed by oceans.
- Decline of the sea ice makes it easier for warm sea water to get underneath glaciers and speed up their flow into the water.
More open water results in stronger storms, causing rainfall and further decline of the snow and ice cover.
- Further decline of the snow and ice cover on Greenland and Antarctica in turn threatens to cause increased releases of methane from Greenland and Antarctica, as described in earlier posts such as this one.

The situation is dire and calls for comprehensive and effective action, as described in the Climate Plan, at: http://arctic-news.blogspot.com/p/climateplan.html

From the post 'Monthly CO₂ not under 400 ppm in 2016', at:
http://arctic-news.blogspot.com/…/monthly-co-not-under-400-…