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Stabilising Climate

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Clive Best

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2016년 12월 12일 오전 4:14

   

In order to stop global warming all we really have to do is to stabilise CO2 emissions, not reduce them to zero!  One of the 'myths' promoted by IPCC climate scientists is that we have to stop burning any fossil fuels i.e. we must 'keep it in the ground'. This is a total fallacy as I will try to explain in this post.

Carbon dioxide sources and sinks must balance once stability is reached

The origin of this belief that we must stop burning all fossil fuels by ~2050 can be traced back to Figure 10 which appeared in the AR5 'Summary for Policy Makers'. Here it is.

Figure 10 from SPM AR5

Figure 10 was intended to send a simple message to the world's political leaders. Namely that there is a finite total amount of fossil fuel that mankind can safely burn, and that we have already burned half of it.  Therefore unless the major industrialised countries stop burning fossil fuels altogether by 2050, the world will warm far above 2C (red curve) causing a global disaster. This message worked, but there is so much wrong about the hidden assumptions and even subterfuge used to produce Figure 10 that I wrote a post about it at the time.

The principal assumptions hidden from view under Fig 10. are:

  1. Carbon sinks are saturating (they are not)
  2. ECS (Equilibrium Climate Sensitivity)  is 3.5C (Uncertain – and could be as low as 1.5C)
  3. Replacement of logarithmic forcing of CO2  with a linear forcing.

As a direct consequence of IPCC successful lobbying based around Figure 10, the Paris treaty now proudly "sets the world on an irreversible trajectory on which all investment, all regulation and all industrial strategy must start to align with a zero carbon global economy". Does anyone really believe that this is even feasible, let alone realistic? It simply is not going to happen because well before then their citizens will revolt and kick them out. The best we can hope for in the short term is a stabilisation in the annual global CO2 emissions.

I argue that by simply stabilising emissions, we can halt global warming. Clearly the lower total 'stable' emissions are then the cooler the planet will be, but even if we only managed to stabilise emissions at current values the net warming will still be <2C and CO2 levels will stop rising and stabilise at <410 ppm.

Atmospheric CO2 levels must always reach an equilibrium as the natural carbon sinks will catch up to balance emissions. For the last 40 years about half of man-made emissions have been absorbed mainly into the oceans, but also into soils and biota. The reason why CO2 levels have been continuously increasing since 1970 is that  we have been increasing emissions each year, so the sinks have never been able to catch up. Sinks will quickly balance emissions and CO2 levels will stop rising once emissions stop increasing. This fact is obvious because run-away CO2 levels have never happened in the earth's long history. Such a balancing mechanism has always stabilised atmospheric CO2 over billions of years during intense periods of extreme volcanic activity, ocean spreading and periodic tectonic mountain building. Fossil fuels are an insignificant fraction when compared to  the buried carbon contained in sedimentary rocks.

To see how this works let's assume that the world can stabilise annual emissions at current rates of 34 Gtons CO2/year  indefinitely. We know that CO2 sinks currently absorb half of that figure – 17 Gtons and have been increasing proportional to the increase in partial pressure of CO2 in the atmosphere – currently 400ppm. Stabilising emissions would result in the increasing fractional uptake by carbon sinks of the now fixed emissions. The remaining fraction of annual emissions that would remain in the atmosphere is therefore as follows.

Year 1: 50%  Year 2: 25% Year 3: 12.5% etc. This is simply equal to the infinite sum

So CO2 levels in the atmosphere will  taper off after just ~10 years to reach a new long term value equivalent to adding an additional 34 Gtons of CO2 to the atmosphere. The atmosphere currently contains 3.13 x 10^12 tons of CO2 so the net increase at equilibrium would be only an extra  1%. Therefore for the years following 2016 the resultant CO2 curve looks like this.

There is also a very good chance that we can achieve such a fixed limit, rather than pretend to meet an impossible target of zero emissions. However this  does mean that CO2 levels will remain at 404 ppm indefinitely, which is far higher than a planet without human beings, but still leaves us plenty of time to replace fossil fuels,  with new nuclear energy.

Controlling CO2 levels by stabilising emissions also has one huge advantage. It means that we can  eventually control the level of 'enhanced global warming' so  avoiding another devastating ice age, otherwise due to begin within 5000 years time.

   

   

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  • 좋은 자료를 공유하고 있는 블로그에서 퍼옴
    .. 정말로 CO2 농도가 평형 상태에 도달하고 유지 할 수 있을지는 ...의심 ..
    ..

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Is the Supermoon responsible for record low Polar ice formation?

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Clive Best

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2016 11 22일 오전 6:09

   

The  "Supermoon"  on November 14th coincided with the closest (perigean) approach to the earth of the moon since 1948. Tidal forces are inversely proportional to the cube of distance. Full moon occurs  when the sun lines up with the moon and November 14th is close to the perigee of the earth's orbit round the sun. This combined to produce strong tides. At full moon in November the moon lies in the southern hemisphere . So for the Arctic it is the opposite facing tides that is strongest while for the Antarctic it is the direct lunar facing tide that dominates. They are symmetric. Here are my calculations of the tractional acceleration at different latitude covering November, based on the JPL ephemeris.

The tractional tidal force acting at 45N (green) and 75N (blue). Polar regions experience far greater tidal ranges during the lunar month than temperature regions. The Supermoon amplified this effect by about 20%. This enhanced tidal mixing and has probably inhibited ice formation since early October.

It is the tidal range that is maximised during a perigean spring tide. That is the difference between low and high tides. At high latitudes this effect is magnified  as just one tide dominates and neap tides effectively disappear completely. This gives an extreme varying monthly tidal range. Tides act throughout the ocean,  dragging both deep  and shallow water alike. This increasing churning tidal flow since October has had two effects. First it has  inhibited natural sea ice formation, and secondly mixed in more warmer water from lower latitudes than normal.  These large tidal ranges look likely to continue till the end of 2016 before returning to normal.

The Arctic ocean also has relatively shallow basins with narrow channels at the Bering Sea and to the North Atlantic between Iceland-Scandinavia. This accentuates tidal flow.

Thanks to @Kata_basis for prompting me to look into this !

see also:

  1. Does the moon trigger interglacials
  2. Evidence of  tidal effect on the polar jet stream
  3. Tidal effects in Polar regions
  4. The straw that broke the camels back

   

   

   

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Lowest amount of sea ice ever seen by humans during...

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The Earth Story

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2016 11 22일 오전 12:00

   

   

Lowest amount of sea ice ever seen by humans during October/November

This week, this remarkable plot began blowing up on social media. The plot tracks global sea ice abundance – a combined measurement of the area covered by ice in both the Arctic and Antarctic. The red line, 2016, shows that Sea Ice extents globally are by far the lowest humans have ever recorded.

Normally at this time of year, Arctic Sea ice is beginning to recover from low volumes reached during the summer, while Antarctic Sea ice is beginning to contract as sunlight falls on that continent. On top of this yearly variation there have been several long-term trends imposed. Most notably, sea ice extents have been decreasing in the Arctic quite regularly for the last 30+ years – the time humans have been actively monitoring sea ice.

The lowest ever extent of sea ice was reached at the end of summer 2012, but that doesn't mean the sea ice has been recovering – instead, years since then have seen record low sea ice values "for specific months". In other words, the long-term trend is gradually decreasing sea ice due to climate change, and records at any time of the year are being broken when a perfect weather pattern hits. One of those weather patterns is hitting in the Arctic right now.

The North Pole right now is already shadowed for the winter. Usually this darkness is associated with plummeting temperatures since no heat from the sun can warm it, but for the past month there have been several times when North Pole temperatures have spiked above the freezing point of water; as much as 15°C above normal for this time of year. These temperatures are being driven by surges of warm air traveling up to the poles from lower latitudes.

Although this effect isn't fully understood yet, warm winter arctic weather combined with surges of colder air traveling south has been a feature of the last several northern hemisphere winters. It has been proposed that these surges are associated with weakening of the jet streams as climate warms – weaken the jet streams, the boundaries between different convection cells in the atmosphere, and it becomes easier for warm air to be pushed all the way up to the poles. So far this fall Siberia has been anomalously cold while the North Pole has been anomalously warm, consistent with this mechanism.

This warm air preventing ice growth also is combining with the low summer sea ice extent. Sea ice is bright and open water is dark, so when sea ice melts the water beneath will store more heat during the summer. 2016 had the 2nd lowest summer sea ice extent observed in the Arctic, so the Arctic Ocean waters are also warmer now than was typical before humans increased greenhouse gas concentrations in the atmosphere.

Meanwhile, the real puzzle this year is the Antarctic. Sea ice in Antarctic has actually been increasing the last few years – a reminder that the Antarctic is a fundamentally different area than the Arctic. In the Antarctic, the presence of the ozone hole has driven more intense winds that have cooled surface waters and helped the formation of Antarctic sea ice. Furthermore, melting on the Antarctic continent has created a supply of fresh water heading into the oceans and fresh water freezes at higher temperature than salty water. Recent work has suggested this could only be a temporary situation – healing of the ozone hole (actually good!) could remove one of the factors protecting Antarctic Sea Ice, and another major factor could be extra warm water at depth. Several recent studies have suggested that Antarctic Sea Ice could be particularly vulnerable to extra warmth in the subsurface – add a bit of extra heat and that ice retreats rapidly.

Right now, there is likely less sea ice on Earth at this time of year than there has been in about a hundred thousand years – going back to before the last cycle of glacial advance. The downward trend, particularly in the Arctic, is extremely likely to continue in future years. It won't always produce an all-time low in September - that takes the perfect weather conditions at the perfect time of year – but when the right weather conditions do show up we'll get record lows for that time of year. Whether this year's rapid sea ice melting in Antarctica will be a one-time event is, as of now, an extremely important question with no good answer.

Sea ice in these areas represents a habitat for many organisms – a stable place where they can rest before heading out into the ocean. As sea ice extents fluctuate, these species are put under increasing threat. Furthermore, the more open ocean there is, the more heat the oceans can take up – so these drops in sea ice can contribute to warming the surrounding oceans and thus put continental ice sheets under even greater stress. Some scientists have been debating whether it is good communication to place all the Earth's sea ice on one chart when both poles are two distinct systems, but the threat to wildlife globally and the effect of warming oceans may represent reasonable worries based on this plot alone.

-JBB

Data credit: NSIDC http://bit.ly/2frYJyk http://bit.ly/1jOd0VZ Read more: http://n.pr/2eBPFLv http://scienceblogs.com/stoat/2016/11/18/sea-ice-wossup/ http://cnn.it/2eRzeKH http://bit.ly/2gnschY

   

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