Why is warming in the Arctic accelerating and where will this lead to?
Where does the extra heat go?
Global warming is causing Earth to heat up. As shown on the image below, by Nuccitelli et al., most heat goes into the oceans.
Warming of water in the Arctic Ocean
White arrows mark ice drift directions. Red arrows mark
the transport path of warm Atlantic water entering the
Arctic where it submerges under the cold, ice-covered
surface layer. Robert Spielhagen (IFM-GEOMAR, Kiel)
Global warming is heating up the oceans big time. As above image shows, the global ocean heat content has been rising for many years.
Water flowing into the Arctic Ocean from the Atlantic Ocean is about 2°C warmer today than it has been for at least 2,000 years, according to a study published in Science. The current of warm water lies 50 metres below the surface, and can reach 6°C in summer — warm compared to Arctic surface waters, which can be -2°C.
At the same time, cold water and sea ice are driven out of the Arctic Ocean, along the edges of Greenland. The net result is a marked increase in the temperature of the water in the Arctic Ocean, especially the top layer of the water which causes the sea ice to melt.
The Arctic radiates comparatively less heat into space
Cold layers of air close to the surface make it difficult for infrared radiation to go out to space, according to a study published in Science. These layers do warm up, but warming of these layers is directed downwards, thus amplifying warming in the Arctic.
Surface air temperatures in the Arctic are rising rapidly
Anomalies for surface air temperatures are higher in the Arctic than anywhere else on Earth. This is illustrated by the interactive images and text in the box at the bottom of this post.
The increase in temperature anomalies appears to be an exponential rise. This is caused not only by the above-described impacts of cold air close to the surface, but also by feedback effects as further described below.
Feedbacks further accelerate warming in the Arctic
One such feedback is albedo change — retreat of Arctic sea ice results in less sunlight being reflected back into space, as further discussed in Albedo Change in the Arctic. Loss of Arctic sea ice is effectively doubling mankind's contribution to global warming. Increased absorption of the sun's rays is the equivalent of about 20 years of additional CO2 being added by man, Professor Peter Wadhams said in a recent BBC article.
One of the most threatening feedbacks is release of methane that are held in the currently frozen seabed. As the seabed warms up, it starts to release methane in what can be rather abrupt ways. Due to methane's high global warming potential, this can further accelerate local warming, triggering further methane releases, in a vicious circle that threatens to spiral into runaway global warming.
Push something and it moves a little. Push it a little more and it moves a little more. This is called a “linearity” response. But sometimes a little push can lead to something totally unexpected! This is called “nonlinearity” and, contrary to what one might think, nonlinearities are inherent in most systems - like our atmosphere, for example. In fact, abrupt and unexpected change happens at some point in most systems - we even have a saying for such unexpected outcomes: a tipping point.
Until recently, our atmosphere and oceans behaved like linear systems: incremental dumping of greenhouse gases into the atmosphere caused incremental changes, like rising temperatures and predictable rates of ice melt. But things are now changing unexpectedly fast – nonlinearity is kicking in! We only have to look at the rapidly vanishing arctic icecap for astonishing evidence.
A few years ago, I felt compelled to leave my previous pursuits in Engineering Physics (and chess master) to begin a PhD thesis focusing on abrupt climate change. I felt the planet’s climate was approaching several tipping points and analysis of Paleoclimatology records (tree rings, ice cores, ocean sediment, etc.) may provide evidence on what tipping points – nonlinearities – we might expect to see first (and maybe prevent).
Sadly, I’m late to the game. The rapidly disappearing Arctic icecap is a tipping point in motion. In all likelihood, statistically speaking, it’s gone, history. Within a few years when the ice disappears entirely, for the first time in 3 (or as many as 13) million years, hold on because our weather patterns will be drastically destabilized. Most folks in my field are still reluctant to acknowledge this 800 pound gorilla staring us right in the face.
Methane, an extremely potent greenhouse gas (105 times more efficient at trapping heat in the atmosphere than carbon dioxide over 20 years, see image left) is a product of ancient wetlands, locked in permafrost and ocean sediments for millions of years. Today, warming air and seawater causes methane to be released more quickly. In the ocean off Siberia, methane plumes greater than one kilometre in diameter have been observed. Shocking stuff in my business.
And other tipping points abound. If the melting Arctic icecap isn’t bad enough, how about persistent droughts turning the Amazon rainforest into dry savannah? Much of the forest would burn first, delivering the double whammy of massive carbon emissions and the loss of a vital carbon sink.
Or how about collapsing boreal forest ecosystems. In Canada, drought-stressed trees, not already under attack by mountain pine beetles and emerald ash borers, would surely burn in the new norm of arid heat waves.
Perhaps the Greenland ice sheet will be the ultimate smoking gun. It contains enough water to raise global sea level by seven metres. With melt rates doubling every few years, knowing what I know, I can honestly say I am gravely concerned. Many models predict Greenland’s ice sheet will be ‘ok’ for another 3 centuries, but as I wrote in my last blog, you can officially pitch those models out the window.
Unlike our ancestors, humanity has a shot at stopping this – that is, if we throw everything we have at it. But we need to urgently focus on doing two things: radically reduce carbon emissions and prevent further warming of the Arctic Ocean; and keep as much methane locked underground as possible (we have the technology to do this today).
We have officially entered the realm of unknown-unknowns; the nonlinearity zone.
The question is will politicians reach the tipping point of reason?
Posted with author's permission. Earlier posted at Sierra Club Canada. Paul Beckwith is a PhD student with the laboratory for paleoclimatology and climatology, department of geography, University of Ottawa.
About 5 million years ago continental drift pushed North and South America together, creating the Isthmus of Panama where the Central American Seaway ocean passage had previously existed. The Pacific and Atlantic were no longer connected, drastically altering global ocean currents and atmospheric circulation patterns. As the Atlantic Gulf Stream strengthened, it carried vast amounts of moisture into the northern regions. The Arctic eventually cooled and it’s estimated sea ice cover has existed continuously in the Arctic Ocean for 3 million years, possibly for as long as 13 million years.
Slow cycling between cold and warm periods occurred on Earth many times due to the planet's changing orbit, tilt, and position relative to the sun. This caused the sea ice to wax and wane in size but it always persisted, never vanishing. Not any longer. The sea ice will disappear for longer and longer periods over the coming years until it is finally gone for good, likely within a decade.
The world will be a different place - just like the world from 3, or even 13, million years ago. No longer will the bright white parasol on the top of the world reflect sunlight and keep the Arctic cool. Dark seawater will absorb light and rapid Arctic warming will quickly decrease temperature gradients between the pole and equator. Jet streams will slow down, meander and change tracks. Storms will change in location, intensity, frequency, and speed and everything that humans know about weather and seasons for growing food will be obsolete. Everything.
Higher global temperatures will cause more evaporation, putting more water vapor into the atmosphere. Condensing into clouds, huge amounts of heat will be released, fueling even larger and more frequent storms.
Throw out the models that project disturbing climate effects in 2100. They're happening now! Already we're seeing rising sea levels from the massive and accelerating Greenland ice melt. The rapid warming of southern oceans is melting and destabilizing Antarctic ice from below, causing enormous chunks to break off (we’ve all seen them on TV). And big increases in Arctic temperatures mean terrestrial permafrost is melting and the now-warmer continental shelf sea floor is releasing increasing amounts of methane gas, a potent climate change gas.
Why is the sea ice getting hammered? Feedback loops. Unknown unknowns
NASA images showing the difference between sea ice cover between 1980 and 2012.
A very rare cyclone churned up the entire Arctic region for over a week in early August, destroying 20% of the ice area by breaking it into tiny chunks, melting it, or spitting it into the Atlantic. Cold fresh surface water from melted sea ice mixed with warm salty water from a 500 metre depth! Totally unexpected. A few more cyclones with similar intensity could have eliminated the entire remaining ice cover. Thankfully that didn't happen. What did happen was Hurricane Leslie tracked northward and passed over Iceland as a large storm. It barely missed the Arctic this time. Had the storm tracked 500 to 600 kilometres westward, Leslie would have churned up the west coast of Greenland and penetrated directly into the Arctic Ocean basin.
We dodged a bullet, at least this year. This luck will surely run out. What can we do about this? How about getting our politicians to listen to climatologists, for starters.
Posted with author's permission. Earlier posted at Sierra Club Canada. Paul Beckwith is a PhD student with the laboratory for paleoclimatology and climatology, department of geography, University of Ottawa.
Andrew Glikson, earth and
paleo-climate scientist at
Australian National University
The linear nature of global warming trends projected by the IPCC since 1990 and as late as 2007 (see Figure 1) has given the public and policy makers an impression there is plenty of time for economies to convert from carbon-emitting industries to non-polluting utilities.
Paleo-climate records suggest otherwise. They display abrupt shifts in the atmosphere/ocean/cryosphere system, as manifest in the ice core records of the last 800,000 years. This suggests high sensitivity of the climate system to moderate changes in radiative forcing, whether triggered by changes in solar radiation energy or the thermal properties of greenhouse gases or aerosols. In some instances these shifts have happened over periods as short as centuries to decades, and even over a few years.
Figure 1: Global surface temperature rise trajectories for the 21st century under varying carbon emission scenarios portrayed by the IPCC AR4 2007. A2 represents the business-as-usual scenario consistent with currently rising global emissions. IPCC
Examples of abrupt climate shifts are the 1470 years-long Dansgaard-Oeschger intra-glacial cycles, which were triggered by solar signals amplified by ocean currents, and the “younger dryas” cold interval, which occured when interglacial peaks resulted in extensive melting of ice and cooling of large ocean regions by melt water.
The last glacial termination (when large-scale melting of ice occurred between about 18,000 to 11,000 years ago) is attributed to transient solar pulsations of 40–60 Watt/m2 affecting mid-northern latitudes. This led to a ~6.5+/-1.5 Watt/m2 rise in mean global atmospheric energy level, which meant a mean global temperature rise of ~5.0+/-1.0 degrees Celsius and sea level rise of 120 meters (see Figure 2).
Figure 2: Comparison between radiative forcing levels of (1) the Pliocene (~400 ppm CO2; T ~ 2-3 degrees C; Sea level 25+/-12 meters higher than pre-industrial); (2) the last Glacial Termination (~6.5+/-1.5 Watt/m2; ~5.0+/-1.0 degrees C; SL rise 120 meters) and (3) Anthropogenic 1750-2007 warming (1.66 Watt/m2 + 1.35 Watt/m2 – the latter currently masked by sulphur aerosols). Modified after Hansen et al 2008
As shown in Figure 2, anthropogenic carbon emission and land clearing since 1750 have raised the atmospheric energy level by +1.66 Watt/m2. Once the masking effect of industrial sulphur aerosols is taken into account. This totals ~3.0 Watt/m2, namely near half the radiative forcing associated with the last glacial termination.
Compounding the major rise in radiative forcing over the last ~260 years is the rate of greenhouse gas (GHG) rise. This has averaged ~0.5ppm CO2 per year since 1750. That’s more than 40 times the rate during the last glacial termination, which was 0.012ppm CO2 per year. The current CO2 rise rate – 2ppm a year – is the fastest recorded for the Cainozoic (the period since 65 million years ago) (see Figure 3).
Figure 3: Relations between CO2 rise rates and mean global temperature rise rates during warming periods, including the Paleocene-Eocene Thermal Maximum, Oligocene, Miocene, glacial terminations, Dansgaard-Oeschger (D-O) cycles and the post-1750 period. Glikson
We have seen this scale and rate of radiative forcing, in particular since the 1970s, expressed by intensification of the hydrological cycle, heat waves and hurricanes around the globe. It imparts a new meaning to the otherwise little-defined term, “tipping point”.
Between 1900 and 2000, the ratio of observed to expected extremes in monthly mean temperatures has risen from ~1.0 to ~3.5. From about 1970 the Power Dissipation Index (which combines storm intensity, duration, and frequency) of North Atlantic storms increased from ~1.0 to ~2.7-5.5 in accord with tropical sea surface temperatures which rose by about 1.0 degree Celsius.
The ostensibly large number of recent extreme weather events has triggered intensive discussions, both in- and outside the scientific community, on whether they are related to global warming. Here, we review the evidence and argue that for some types of extreme — notably heat waves, but also precipitation extremes — there is now strong evidence linking specific events or an increase in their numbers to the human influence on climate. For other types of extreme, such as storms, the available evidence is less conclusive, but based on observed trends and basic physical concepts it is nevertheless plausible to expect an increase.
Hansen et al analysed the distribution of anomalous weather events relative to the 1951–1980 base line, displaying a shift toward extreme heat events (see Figure 4). The authors observe:
hot extreme[s], which covered much less than 1% of Earth’s surface during the base period (1951-1980), now typically [cover] about 10% of the land area. It follows that we can state, with a high degree of confidence, that extreme anomalies such as those in Texas and Oklahoma in 2011 and Moscow in 2010 were a consequence of global warming because their likelihood in the absence of global warming was exceedingly small.
Figure 4: Hansen et al 2012 calculate the seasonal mean and standard deviation at each grid point for this period, and then normalize the departures from the mean, obtaining a Gaussian bell-shaped distribution. They plot a histogram of the values from successive decades, getting a sense for how much the climate of each decade departed from that of the initial baseline period. The shift in the mean of the histogram is an indication of the global mean shift in temperature, and the change in spread gives an indication of how regional events would rank with respect to the baseline period. Hansen et al
The consequences for the biosphere of accelerating climate change are discussed by Baronsky et al in the following terms:
Localized ecological systems are known to shift abruptly and irreversibly from one state to another when they are forced across critical thresholds. Here we review evidence that the global ecosystem as a whole can react in the same way and is approaching a planetary-scale critical transition as a result of human influence.
Climates found at present on 10–48% of the planet are projected to disappear within a century, and climates that contemporary organisms have never experienced are likely to cover 12–39% of Earth. The mean global temperature by 2070 (or possibly a few decades earlier) will be higher than it has been since the human species evolved.
At 400ppm CO2, potential climate conditions have reached levels which last existed in the peak Pliocene epoch (5.3-2.6 million years ago). Given an increase in extreme weather events under conditions of +0.8C, an even higher rate of extreme events is expected under conditions of +2.0C currently shielded by industrially emitted sulphur aerosols.
Current trends in the frequency and intensity of extreme weather events are evident globally (see Figure 5). In the USA, the number of meteorological, hydrological and climatological events rose from about 20-40 per year during 1980-1988, to about 40-80 per year during 1989-2005, to between 70-100 per year after 2006, consistent with global rise in the frequency of extreme weather events.
Figure 5: Global frequency of natural disaster impacts and associated human and economic losses from the 1970s to 1990s. World Meteorological Organization, 2006 http://www.nrcan.gc.ca/earth-sciences/climate-change/community-adaptation/assessments/378 James Hansen states:
There is still time to act and avoid a worsening climate, but we are wasting precious time. We can solve the challenge of climate change with a gradually rising fee on carbon collected from fossil-fuel companies, with 100% of the money rebated to all legal residents on a per capita basis. This would stimulate innovations and create a robust clean-energy economy with millions of new jobs. It is a simple, honest and effective solution.
New solar technologies promise to provide a large part of the answer. Time is of the essence.
Andrew Glikson is Honorary Professor at the Geothermal Energy Centre of Excellence, The University of Queensland, and a Visiting Fellow at the Australian National University.
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