Showing posts with label Samantha Bova. Show all posts
Showing posts with label Samantha Bova. Show all posts

Sunday, June 13, 2021

Could temperatures keep rising?

Orbital changes are responsible for Milankovitch cycles that make Earth move in and out of periods of glaciation, or Ice Ages. Summer insolation on the Northern Hemisphere reached a peak some 10,500 years ago, in line with the Milankovitch cycles, and insolation has since gradually decreased.
Summer insolation on the Northern Hemisphere in red and in langleys
per day (left axis, adapted from Walker, 2008). One langley is 1 cal/cm²
(thermochemical calorie per square centimeter), or 41840 J/m² (joules
per square meter), or about 11.622 Wh/m² (watt-hours per square meter). 
In blue is the mean annual sea surface temperature, given as the difference
from the temperature over the last 1000 years (right axis, from Bova, 2021).

Snow and ice cover acting as a buffer

While temperatures rose rapidly, especially before the insolation peak was reached, the speed at which temperatures rose was moderated by the snow and ice cover, in a number of ways:
  • snow and ice cause sunlight to get reflected back into space
  • energy from sunlight is consumed in the process of melting snow and ice, and thawing permafrost
  • meltwater from sea ice and runoff from melting glaciers and thawing permafrost cools oceans.
In other words, the snow and ice cover acted as a buffer, moderating the temperature rise. While this buffer has declined over time, it is still exercizing this moderation today, be it that the speed at which this buffer is reducing in size is accelerating, as illustrated by the image below, showing the rise of the sea surface temperature on the Northern Hemisphere.

[ from earlier post ]

Will the snow and ice cover ever grow back?

More recently, the temperature rise has been fueled by emissions caused by people. While emission of greenhouse gases did rise strongly since the start of the Industrial Revolution, the rise in emission of greenhouse gases by people had already started some 7,000 years ago with the rise in modern agriculture and associated deforestation, as illustrated by the image below, based on Ruddiman et al. (2015).


The temperature has risen accordingly since those times. At the start of the Industrial Revolution, as the image at the top shows, temperatures already had risen significantly, compared to some 6000 years before the Industrial Revolution started. When also taking into account that the temperature would have fallen naturally (i.e. in the absence of these emissions), the early temperature rise caused by people may well be twice as much.

Temperatures could keep rising for many years, for a number of reasons:
  • Snow & Ice Cover Loss - A 2016 analysis by Ganapolski et al. suggests that even moderate anthropogenic cumulative carbon dioxide emissions would cause an absence of the snow and ice cover in the next Milankovitch cycle, so there would be no buffer at the next peak in insolation, and temperatures would continue to rise, making the absence of snow and ice a permanent loss.
  • Brighter Sun - The sun is now much brighter than it was in the past and keeps getting brighter.
  • Methane - Due to the rapid temperature rise, there is also little or no time for methane to get decomposed. Methane levels will skyrocket, due to fires, due to decomposition of dying vegetation and due to releases from thawing of terrestrial permafrost and from the seafloor as hydrates destabilize.
  • No sequestration - The rapidity of the rise in greenhouse gases and of the associated temperature rise leaves species little or no time to adapt or move, and leaving no time for sequestration of carbon dioxide by plants and by deposits from other species, nor for formation of methane hydrates at the seafloor of oceans.
  • No weathering - The rapidity of the rise also means that weathering doesn't have a chance to make a difference. Rapid heating is dwarfing what weathering can do to reduce carbon dioxide levels. 
  • Oceans and Ozone Layer Loss - With a 3°C rise, many species including humans will likely go extinct. A 2013 post warned that, with a 4°C rise, Earth will enter a moist-greenhouse scenario. A 2018 study by Strona & Bradshaw indicates that most life on Earth would disappear with a 5°C rise. As temperatures kept rising, the ozone layer would disappear and the oceans would keep evaporating and eventually disappear into space, further removing elements and conditions that are essential to sustain life on Earth.

Paris Agreement

All this has implications for the interpretation of the Paris Agreement. At the Paris Agreement, politicians pledged to take efforts to ensure that the temperature will not exceed 1.5°C above pre-industrial levels.

So, what is pre-industrial? To calculate how much the temperature has risen, let's start at 2020 and go back one century. According to NASA data, the temperature difference between 1920 and 2020 is 1.29°C (image below). 


The NASA ocean data are for sea surface temperatures, so another 0.10°C can be added to obtain global air near surface temperatures (2 m). Furthermore, it makes sense to add another 0.10°C for higher polar anomalies. This would bring the temperature rise from 1920 up to 1.49°C.  


Of course, 1920 is not pre-industrial. As the IPCC mentions, the 'pre-' in pre-industrial means 'before', implying that 'pre-industrial' refers to levels as they were in times well befóre (as opposed to when) the Industrial Revolution started.

When taking the rise over the past century and adding 0.30°C for the rise over the previous 170 years, that brings the rise up to 1.79°C (from ≈1750, the start of the Industrial Revolution). Carbon dioxide and methane levels started to rise markedly about 6000 years ago, causing a 0.29°C rise for the years from 3480 BC to 1520 (see image at top). Finally, there will also have been a rise for the years from 1520 to 1750 that, when estimated at 0.20°C, would mean that emissions by people could have caused the temperature to rise by 2.28°C (4.122°F), compared to the temperature some 5500 years ago (see inset on above image).

A huge temperature rise by 2026?

A recent post suggests that the 1.5°C threshold was already crossed in 2012, i.e. well before the Paris Agreement was adopted by the U.N. (in 2015), while there could be a temperature rise of more than 3°C by 2026.

Such a rise could be facilitated by a number of events and developments, including:

[ from earlier post see CH4 GWP]
• The Arctic sea ice latent heat tipping point and the seafloor methane hydrates tipping point look set to get crossed soon (see above image).

• Continued emissions. Politicians are still refusing to take effective action, even as greenhouse gas emissions appear to be accelerating. The warming impact of carbon dioxide reaches its peak a decade after emission, while methane's impact over a few years is huge.

• Sunspots. We're currently at a low point in the sunspot cycle. As the image on the right shows, the number of sunspots can be expected to rise as we head toward 2026, and temperatures can be expected to rise accordingly. According to James Hansen et al., the variation of solar irradiance from solar minimum to solar maximum is of the order of 0.25 W/m⁻².

• Temperatures are currently also suppressed by sulfate cooling, and their impact is falling away as we progress with the necessary transition away from fossil fuel and biofuel, toward the use of more wind turbines and solar panels instead. Aerosols typically fall out of the atmosphere within a few weeks, so as the transition progresses, this will cause temperatures to rise over the next few years.

• El Niño events, according to NASA, occur roughly every two to seven years. As temperatures keep rising, ever more frequent strong El Niño events are likely to occur. NOAA anticipates the current La Niña to continue for a while, so it's likely that a strong El Niño will occur between 2023 and 2025.

• Rising temperatures can cause growth in sources of greenhouse gases and a decrease in sinks, as discussed in an earlier post.

The mass extinction event that we are currently in is rapidly progressing, even faster than the Great Permo-Triassic Extinction, some 250 million years ago, when the temperature rose to about 28°C, i.e. some 14.5°C higher than pre-industrial.

In the video below, Guy McPherson discusses the current mass extinction.


In the video below, Ye Tao introduces and discusses the MEER ReflEction idea.


In conclusion, there could be a huge temperature rise by 2026 and with a 3°C rise, humans will likely go extinct, which is a daunting prospect. Even so, the right thing to do is to help avoid the worst things from happening, through comprehensive and effective action as described in the Climate Plan.


Links

• Climate change and ecosystem response in the northern Columbia River basin - A paleoenvironmental perspective - by Ian R. Walker and Marlow G. Pellat (2008)
https://cdnsciencepub.com/doi/10.1139/A08-004

• Vance, R.E. 1987. "Meteorological Records of Historic Droughts as Climatic Analogues for the Holocene." In N.A. McKinnon and G.S.L. Stuart (eds), Man and the Mid-Holocene Climatic Optimum - Proceedings of the Seventeenth Annual Conference of the Archaeological Association of the University of Calgary. The University of Calgary Archaeological Association, Calgary: 17-32.

• Seasonal origin of the thermal maxima at the Holocene and the last interglacial - by Samantha Bova et al. (2021)
https://www.nature.com/articles/s41586-020-03155-x

• Palaeoclimate puzzle explained by seasonal variation (2021)
https://www.nature.com/articles/d41586-021-00115-x

• Important Climate Change Mystery Solved by Scientists (news release 2021)
https://www.rutgers.edu/news/important-climate-change-mystery-solved-scientists

• Milankovitch (Orbital) Cycles and Their Role in Earth's Climate - by Alan Buis (NASA news, 2020)
https://climate.nasa.gov/news/2948/milankovitch-orbital-cycles-and-their-role-in-earths-climate

• Milankovitch cycles - Wikipedia
https://en.wikipedia.org/wiki/Milankovitch_cycles

• Insolation changes
https://energyeducation.ca/encyclopedia/Insolation
http://www.geo.umass.edu/faculty/bradley/bradley2003x.pdf

• Late Holocene climate: Natural or anthropogenic? - by William Ruddiman et al. (2015)
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015RG000503

• Critical insolation–CO2 relation for diagnosing past and future glacial inception - by Andrey Ganapolski et al. (2016)
https://www.nature.com/articles/nature16494

• Co-extinctions annihilate planetary life during extreme environmental change - by Giovanni Strona & Corey Bradshaw (2018)

• Earth is on the edge of runaway warming
https://arctic-news.blogspot.com/2013/04/earth-is-on-the-edge-of-runaway-warming.html

• Paris Agreement
https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement
https://unfccc.int/sites/default/files/english_paris_agreement.pdf

• IPCC Special Report: Global warming of 1.5 ºC — Box SPM.1: Core Concepts 
https://www.ipcc.ch/sr15/chapter/spm/

• IPCC AR5 Synthesis Report — Figure 2.8
https://www.ipcc.ch/report/ar5/syr/synthesis-report

• IPCC AR5 Report, Summary For Policymakers
https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_SPM_FINAL.pdf

• NASA Analysis Graphs and Plots - LSAT and SST change

• Most Important Message Ever
https://arctic-news.blogspot.com/2019/07/most-important-message-ever.html

• Radiative forcing of carbon dioxide, methane, and nitrous oxide: A significant revision of the methane radiative forcing - by M. Etminan et al.
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016GL071930

• When Will We Die?
https://arctic-news.blogspot.com/2019/06/when-will-we-die.html

• Possible climate transitions from breakup of stratocumulus decks under greenhouse warming - by Tapio Schneider et al.
https://www.nature.com/articles/s41561-019-0310-1

• A World Without Clouds
https://www.quantamagazine.org/cloud-loss-could-add-8-degrees-to-global-warming-20190225

• How close are we to the temperature tipping point of the terrestrial biosphere? - by Katharyn Duffy et al.

• What Carbon Budget?


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Thursday, January 28, 2021

What Carbon Budget?


Orbital changes are responsible for the Milankovitch cycles that make Earth move in and out of periods of glaciation, or Ice Ages. In line with these cycles, July insolation has slowly decreased over the last 12,000 years. While insolation was at a peak some 12,000 years ago, temperatures rose only slowly at first, as the ice receded that was formed during the most recent Ice Age.

Some previous temperature reconstructions did suggest that a peak on temperature was reached around 6,000 to 7,000 years ago, followed by a decrease in temperature that continued until the industrial age. However, Samantha Bova and colleagues found that most of the records used in such reconstructions represented seasonal temperatures rather than annual ones.

They developed a method of evaluating individual records for seasonal bias and after adjusting for this, they found that the mean annual sea surface temperature has been rising steadily for the past 12,000 years, due to retreating ice sheets during the period from 12,000 to 6,500 years ago and, more recently, due to the increase in greenhouse gas emissions.

Paris Agreement

The Paris Agreement calls for a global average temperature well below 2°C above pre-industrial levels, with efforts taken to ensure that the temperature doesn't exceed 1.5°C above pre-industrial levels.

So, what are pre-industrial levels? The 'pre-' in pre-industrial means before, suggesting that pre-industrial levels refers to levels as they were in times before the Industrial Revolution started.

While emission of greenhouse gases did rise strongly since the start of the Industrial Revolution, the rise in emission of greenhouse gases by people had already started some 7,000 years ago with the rise in modern agriculture and associated deforestation. As this new study shows, the temperature has risen steadily since.

A recent post confirms earlier warnings that the temperature may already have risen by more than 2°C, and it looks even more that way when moving the baseline back 7,000 years. Moreover, this recent post again warns that the temperature rise is accelerating as tipping points are getting crossed, feedbacks are growing stronger and further heating elements are kicking, all interacting in non-linear ways to speed up the temperature rise.

So, where are those efforts that politicians pledged they would be taking?

What Carbon Budget?

Instead of making a genuine effort, most politicians and mainstream media keep telling people that there was a carbon budget to be divided among polluters, as if people should happily continue to consume the polluting products that are pushed by advertisers, for decades to come.

In reality, however, there is no carbon budget, there is no pollution budget. Instead, there is just a huge pollution debt to be paid and every minute of delay causes exponential growth of this debt and of the prospect of rapid human extinction and ultimately extinction of all life on Earth.


Carbon dioxide levels

[ click on images to enlarge ]
The IPCC image on the right shows CO₂ concentrations (up to 2000 ppm) and, underneath, the temperature rise (relative to 1986-2005) for the various RCPs.

What is RCP2.6? As the IPCC described in AR5, the temperature does not rise above 1.5°C (relative to 1850-1900) under the RCP2.6 scenario, and CO₂ concentrations do not rise above 421 ppm.

It looks like CO₂ concentrations will soon cross this 421 ppm threshold, given that the average daily CO₂ level recorded at Mauna Loa, Hawaii, was 419.12 ppm on February 4, 2021, a record high. The next day, February 5, 2021, the daily level was even higher, 419.45 ppm. The annual peak is typically reached in May, so levels can be expected to rise further over the next few months and cross the 421 ppm threshold soon.
 
Crossing the 421 ppm threshold implies that the RCP2.6 scenario is no longer applicable and that politicians won't be able to honour the pledges made at the Paris Agreement without geoengineering.

How much could temperatures rise? The IPCC image shows that the IPCC at the time when AR5 was written expected the temperature to rise by 3.7°C (with a range of 2.6°C to 4.8°C) under RCP8.5 by 2081–2100 relative to 1986–2005, and to keep rising beyond 2100 and reach 7.4°C and possibly 9.4°C relative to 1986–2005 over time.

The IPCC adds that, by 2100, CO₂ concentrations would reach 936 ppm under RCP 8.5., but when also (next to CO₂ concentrations) including the prescribed concentrations of CH₄ and N₂O, the combined CO₂-equivalent concentrations for RCP8.5 is expected to rise to 1313 ppm by the year 2100.

Meanwhile, a study discussed in an earlier post found that when the 1200 ppm CO₂-e gets crossed, the clouds feedback starts to kick in that can push the temperature up by an additional 8°C.

In line with IPCC AR5 figures, methane's Global Warming Potential (GWP) over a few years is 150.

Since AR5 was published, a study found methane's 100 year GWP to be 14% higher than the IPCC value. When applying an extra 14% to methane's short-term GWP of 150, it rises to 171.

Let's take the above (February 5, 2021) CO₂ level of 419.45 ppm and add the WMO 2019 level of methane of 1877 ppb, which with a short-term GWP of 171 translates into heating equivalent of 320.967 ppm CO₂.

Together, the existing CO₂ and methane add up to 740.417 ppm CO₂e, which is 459.583 ppm CO₂e away from the 1200 ppm CO₂e cloud tipping point.

In other words, a methane burst alone could drive up the methane level in the atmosphere by 2688 ppb, resulting in the cloud feedback tipping point to get crossed and the temperature to rise by an additional 8°C. Alternatively, the 1200 ppm CO₂e tipping point could get crossed due to a combination of warming elements, as depicted in the chart below, from a recent post, which would result in a total rise of 18°C when the cloud feedback is added on top. 



Methane

A reduction in carbon dioxide levels in the atmosphere isn't the only thing that's needed to avoid the worst of the looming temperature rise. There are many further lines of action that need to be implemented urgently, including efforts to reduce methane levels. 

Ominously, high methane levels were recorded by the N20 satellite on the morning of January 20, 2021. The combination image below shows levels as high as 2636 ppb at 695 mb (panel left) and 2806 ppb at 487 mb (panel right).


High methane levels were also recorded on January 30, 2021 pm. The combination image below shows that the SNPP satellite recorded levels as high as 2704 ppb at 487 mb (panel left), while the MetOp-2 satellite recorded levels as high as 2344 ppb at 469 mb (panel right). 


On February 4, 2021 pm, the MetOp-1 satellite recorded methane levels of 3071 ppb at 469 mb, as illustrated by the image in the right.

High peak methane levels are very worrying; what makes it even more threatening is that so much of the Arctic Ocean on above images is showing to be covered by high methane levels. 

This supports fears expressed earlier, such as in this recent post, about methane's present and future role in accelerating the temperature rise. 

Nitrous oxide

The image on the right shows nitrous oxide levels at Barrow, Alaska, over the past few years. 

Clearly, action to avoid nitrous oxide releases is also needed urgently.  

Conclusion

The situation is dire and calls for immediate, comprehensive and effective action as described in the Climate Plan.


Links

• Seasonal origin of the thermal maxima at the Holocene and the last interglacial - by Samantha Bova et al.
https://www.nature.com/articles/s41586-020-03155-x

• Palaeoclimate puzzle explained by seasonal variation
https://www.nature.com/articles/d41586-021-00115-x

• Important Climate Change Mystery Solved by Scientists
https://www.rutgers.edu/news/important-climate-change-mystery-solved-scientists

• Milankovitch (Orbital) Cycles and Their Role in Earth's Climate - by Alan Buis (NASA news, 2020)
https://climate.nasa.gov/news/2948/milankovitch-orbital-cycles-and-their-role-in-earths-climate

• Milankovitch cycles - Wikipedia
https://en.wikipedia.org/wiki/Milankovitch_cycles

• Insolation changes
https://energyeducation.ca/encyclopedia/Insolation
http://www.geo.umass.edu/faculty/bradley/bradley2003x.pdf

• Paris Agreement
https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement
https://unfccc.int/sites/default/files/english_paris_agreement.pdf

• IPCC AR5 Synthesis Report — Figure 2.8
https://www.ipcc.ch/report/ar5/syr/synthesis-report

• IPCC AR5 Report, Summary For Policymakers
https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_SPM_FINAL.pdf

• Most Important Message Ever
https://arctic-news.blogspot.com/2019/07/most-important-message-ever.html

• Radiative forcing of carbon dioxide, methane, and nitrous oxide: A significant revision of the methane radiative forcing - by M. Etminan et al. 

• Possible climate transitions from breakup of stratocumulus decks under greenhouse warming - by Tapio Schneider et al.
https://www.nature.com/articles/s41561-019-0310-1

• A World Without Clouds
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