The beginning of the Anthropocene, the period when humanity became the predominant driver of changes in the Earth Systems, has been open to debate. Some argue for the period of the post-WW2 Great Acceleration, others for the beginning of industrialization, and some would perhaps go back as far as the European conquest and colonization of the rest of the world. What few seem to grasp is that the Anthropocene may last but a few decades, until the Earth responds like a boulder rolling down a hill. Humanity provided the push that overcame its inertia, but once in motion it accelerates away all by itself.
To exit the Anthropocene is to enter a period where humanity will be incapable of doing anything meaningful to stop climatic changes. Paleoclimatological research has shown that the Earth can jump up and sprint like a Gazelle at tipping points, with such things as one degree per year temperature increases, and feet of sea level rise per decade. Once started, these will be far too fast for society to reverse, it will simply have to adapt or even just struggle to survive. This is what scientists refer to as Abrupt Climate Change.
While the evidence that the door to the end of the Anthropocene is opening wide mounts, our society seems unable to grasp the scale and urgency of the danger. At the level of the United Nations, we have “soft” denial; an acceptance that climate change is real, but an assumption that the rate of change will be relatively slow and linear. It can be dealt with by some tweaks to the way our societies are currently run, nothing too unsettling required. And anyway, any overshooting of carbon dioxide levels can always be dealt with by new technology to suck it out of the air and safely store it. “We have the technology”. Then there are the “hard” deniers, personified by President Trump, who seem intent on the destruction of any public institutions that deliver inconvenient facts such as those that confirm the reality of climate change. It is as if the crew of the Titanic was split between those that thought that it would take days to sink, and those that believed that it would never sink. No need to panic, better to relax with a nice cup of tea.
The Arctic: The Canary In The Earth System
Miners used to take a canary down into the earth with them. As the canary was more susceptible to the effects of carbon monoxide and methane than humans, it would die well before the humans were overcome; allowing them to escape in time. Climatologists talk about Arctic Amplification, the greater response of the Arctic region to climate change than other parts of the planet. With temperatures now regularly 20 degrees centigrade above normal in parts of the Arctic it is apparent that it has already entered a period of abrupt climate change. It has been estimated that the effect of the reduction in sea ice and snow in the region, experienced by 2010, was already equal to 25% of human-driven climate change. The reflective white snow and ice had been replaced by dark water and ground that take in much more of the Sun’s energy, rather than reflect it back out to space. Since 2010, the sea ice has continued its decline. No theoretical models are required to understand the pace of change, just the ability to fit a curve to the monthly observations, as Wipneus provides each month.
As sea ice is a three dimensional entity, it’s important to track volume rather than surface area. The volume has been showing a much worse picture than area, as the ice has thinned considerably. Soon that reduction in volume will be matched by a rapid decline in area that will provide much larger expanses of dark water to suck in the Sun’s energy. Researchers have estimated that if the Arctic became ice-free for the month of September only in 2040, the extra energy that would be taken in would equal half of the current carbon budget. They should perhaps get away from the climate models and look at Wipneus’ graphs, the early 2020’s may be a much more reasonable time for an ice-free September. By itself, that would more than negate the currently assumed carbon budget.
With a feedback loop of more open water = more heat = more ice melt = more open water, an ice free September would be followed by August, July and then June. The Sun’s energy hitting the Arctic is many times greater at the height of the summer, so things will only get worse as more and more ice is gone in June. It had been assumed that extra reflective clouds would appear over the open water, making up for the lack of sea ice, but recent observations seem to contradict that. The extra cloudiness has mainly been seen in the fall, not the summer, when it acts as a blanket to keep the heat in by reflecting much of it back to Earth. The extra heat that would be taken in by an ice-free Arctic from June onwards is quite possibly greater than that captured by all man-made carbon emissions. Stop and think about that statement. “Abrupt” really doesn’t do it justice.
With that heating concentrated in the Arctic, rather than spread across the world, it will play havoc with structure of the climate and our weather systems. The slow march northward of the northern Hadley Cell assumed by the United Nations may turn into a chaotic interaction between the Hadley, Ferrel and Polar Cells, removing the predictability required by our farmers to grow our food. The increasing weakening and meandering of the Jet Stream, that separates the Polar Cell from the rest of the Northern Hemisphere, has already been observed for the past few years. As the Arctic warms more than the rest of the Northern Hemisphere, the temperature differential that drives the Polar Jet Stream is reduced. The effect will also be felt in the Southern Hemisphere, as a warmer Northern Hemisphere will force more of the heat taken in at the Equator southwards.
The breakdown of the Jet Stream also acts as a positive feedback for the Arctic, as storms from the south find it easier to enter the polar region. They bring both extra heat and extra moisture into the region, both of which reduce the thickness of sea ice. An example is that of Storm Frank in 2015 that thinned and shrank the sea ice cover in the middle of the Arctic winter. With open waters, and even thinner stretches of ice, such storms also churn the sea up. This both mechanically attacks the ice, and allows warmer water from below to be brought to the surface.
Increased Natural Carbon Emissions
Within the Earth Systems, there is ongoing cycling of carbon between the land, oceans and atmosphere. Prior to humanity adding extra carbon emissions, this process had been balanced – with the level of carbon dioxide in the atmosphere varying little from year to year, for at least 10,000 years. This was the period of the Holocene that encompasses all of modern human history; from the first small settlements to the mega-cities of today. As temperatures rise, due to human emissions, the rate of natural emissions can increase and the rate of uptake from the sinks reduce. Permafrost melts releasing its stored carbon, forests decline, and peat bogs increase their output of carbon dioxide, etc. Recent research and observations point to these processes starting to have a significant effect , which will tend to offset reductions in human emissions.
Assumptions that the increased levels of carbon dioxide will increase the level of plant growth, driving up the storage of carbon and increasingly offsetting human emissions, have come under challenge. Recent research points to a relatively small temperature range in which a given plant flourishes, that will limit such extra growth. In addition, other variables such as the availability of water, will serve to limit the beneficial effect of extra carbon dioxide. There is also the possibility that deforestation is moving towards a critical point in some areas, where the forest may collapse.
The Boulder Is Starting To Tip Over – Exiting The Anthropocene
We are close to the point where the Earth will tip over and start rolling by itself, ending the short Anthropocene. After which humanity will be turned back into an observer of changes in Earth Systems, rather than a remaker of those systems. The need for rapid changes in the way that we run our societies, and the acceptance that the old geographical and climatic certainties may rapidly change, is needed. The thought that we can simply geo-engineer our way out of trouble may be proven to be the naiveté of a still young civilization.
 NOAA (2017), Arctic Report Card: Update for 2016, NOAA. Accessible at http://arctic.noaa.gov/Report-Card/Report-Card-2016/ArtMID/5022/ArticleID/271/Surface-Air-Temperature
 Wipneus (2017), PIOMAS Monthly Average Arctic Ice Volume with exponential trend, Wipneus. Accessible at https://sites.google.com/site/arctischepinguin/home/piomas/grf/piomas-trnd2.png
 Mikel Gonzalez-Aquino et. al. (2017), Mitigation implications of an ice-free summer in the Arctic Ocean, Earth’s Future. Accessible at http://onlinelibrary.wiley.com/doi/10.1002/2016EF000429/full
 NASA (2016), Clouds and Sea Ice: What Satellites Show About Arctic Climate Change, NASA. Accessible at https://www.nasa.gov/feature/langley/clouds-and-sea-ice-what-satellites-show-about-arctic-climate-change
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 NASA (2016), Extremely Warm 2015-’16 Winter Cyclone Weakened Arctic Sea Ice Pack, NASA. Accessible at https://www.nasa.gov/feature/goddard/2016/extremely-warm-2015-16-winter-cyclone-weakened-arctic-sea-ice-pack
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