4 ms·

What are the implications of 'irreversible'? Practically irreversible? Cannot be reversed naturally? If we run out of ice, what's to say cooling down the planet

What are the implications of 'irreversible'? Practically irreversible? Cannot be reversed naturally? If we run out of ice, what's to say cooling down the planet by halting carbon production won't recreate the ice caps?

PeterisP 7y ago
The implications of 'irreversible' are that it's going to become much more difficult to reverse in the "short term" (less than hundreds of years) as after the various tipping points reversing would involve not only to cancel/compensate for our emissions, but also to overcome the much larger positive feedback loops e.g. methane released by melting permafrost, increased solar absorbtion/heating after the reflective icecaps melt, etc. It's not technically irreversible, however, the point is that however expensive and difficult prevention might seem, reversing it after the temperature increase is going to be much, much more expensive and difficult. And our capacity to do stuff is going to decrease as we suffer from the consequences - e.g. population reduction, conflicts, etc.
- wolfgke 7y ago
  > And our capacity to do stuff is going to decrease as we suffer from the consequences - e.g. population reduction, conflicts, etc. If the population reduces, the emission of greenhouse gases decrease which helps to reverse the effect of climate change.
  - PeterisP 7y ago
    These feedback loops are in total larger than our emissions, so once we hit them in the coming decades, the global warming would continue increasing for at least a few centuries even if all humans would be dead and make zero emissions. Hitting zero emissions now (which IMHO is unrealistic) would stop global warming at something like +2C level. Hitting zero emissions in 2050 will still mean a runaway global warming, and fixing that would require some effects that go way beyond zero emissions e.g. large scale carbon sequestration (effectively negative emissions), geoengineering sci-fi or something like that. In 1980 it would have been sufficient to "just" reduce the growth.
sleepysysadmin 7y ago
You will find that predictions of climate change have been 100% false. Nobody has a crystal ball and nobody can predict what will happen in the future. So lets look into the past. https://en.wikipedia.org/wiki/Geologic_temperature_record#/media/File:All_palaeotemps.svg https://en.wikipedia.org/wiki/Geologic_temperature_record#/m... About 20,000 years ago the earth was 10 celcius colder. For the last 20,000 years the earth has been warming pretty steadily. About 100,000 years ago the world was 5celcius warmer than today. If you look at the black/red dots from the IPCC predictions. All of those have already been disproven as false and not going to happen. Overall on the graph what's happening is that we are more or less exactly flat. However look at those spikes: https://en.wikipedia.org/wiki/Eemian#/media/File:EPICA_delta_D_plot.svg https://en.wikipedia.org/wiki/Eemian#/media/File:EPICA_delta... Temperature on earth frequently rapidly spiked up in temperature. So what happened to life on earth when it was 5+ celcius warmer? It was fantastic for life. Frozen wastelands like Canada and Russia thawed and became extremely livable. People moved into these northern places. https://en.wikipedia.org/wiki/Eocene https://en.wikipedia.org/wiki/Eocene The Eocene 50 million years ago was 14celcius warmer and life thrived better than no other time in history.
- gjm11 7y ago
  > predictions of climate change have been 100% false That statement is itself 100% false, so far as I can tell. Here's one example. In 1982, some of Exxon's scientists wrote a memo for their management containing a graph (figure 3, page 7, of http://www.climatefiles.com/exxonmobil/1982-memo-to-exxon-management-about-co2-greenhouse-effect/ http://www.climatefiles.com/exxonmobil/1982-memo-to-exxon-ma...) saying that by 2020 CO2 levels would be in roughly the range 400..430 ppm and global mean temperature would be up by roughly 1..1.3 degrees C compared to 1960. Here we are in 2020 and the figures are about 410ppm and +0.9 degrees C. That matches up pretty well, wouldn't you say? > For the last 20,2000 years the earth has been warming pretty steadily What the graph you yourself linked to shows is something very different. There are wild oscillations in the Pleistocene (i.e., before 20k years ago), ending up with temperatures much colder than the present. Then a rapid increase from 20k to 10k years ago. Then near-flat temperatures for the last 10k years. And -- though it's over so short a period that it's hard to see on that graph -- an extremely rapid increase over the last ~50 years. > All of those have already been disproven as false and not going to happen How? By whom? > we are more or less exactly flat This https://climate.nasa.gov/vital-signs/global-temperature/ https://climate.nasa.gov/vital-signs/global-temperature/ is not what I would call "more or less exactly flat". > look at those spikes ... frequently rapidly spiked up in temperature You're looking at a portion of the Pleistocene, also known as the last Ice Age. Glaciers came and went, and the Eemian "spike" is one of those periods in which the glaciers melted. So, yes, indeed, temperatures "spiked up" and we had a transition from a large fraction of the earth's land area being covered in ice to hardly any of it being. Are you suggesting that we shouldn't be worried about climate change because the consequences might not be any more severe than those of the melting of an ice sheet covering the whole of Canada? > it was fantastic for life Pretty good for life overall, yes, and the climate change we're causing might be too. However, my own interests are parochial enough that I care much more what happens to our species and the others that we've grown to depend on, which is any entirely different question. For instance ... > The Eocene 50 million years ago was 14 celsius warmer and life thrived ... 50M years ago, sea levels were something like 100m higher than they are now. There's a handy tool at http://www.floodmap.net/ http://www.floodmap.net/ that lets you explore the consequences of a given increase in sea level (though it's a bit glitchy and it looks like maybe it doesn't have data for anything too far from the equator). At 100m, things we would lose include: about half of England and Ireland; all of the Netherlands; half of Belgium; most of western France; all of Senegal, the Gambia, and Guinea-Bissau; huge amounts of the eastern USA including more or less all of Florida, Louisiana, Delaware and Rhode Island. I'm sure life would thrive. The human race would adapt too, no doubt; we're a very adaptable species. But a whole lot of us would have our homes under water, and large regions of what's now the inhabitable world would become inhospitable to human life. E.g., a temperature rise of 14 degrees C turns San Francisco into Death Valley.

PeterisP 7y ago

The implications of 'irreversible' are that it's going to become much more difficult to reverse in the "short term" (less than hundreds of years) as after the various tipping points reversing would involve not only to cancel/compensate for our emissions, but also to overcome the much larger positive feedback loops e.g. methane released by melting permafrost, increased solar absorbtion/heating after the reflective icecaps melt, etc. It's not technically irreversible, however, the point is that however expensive and difficult prevention might seem, reversing it after the temperature increase is going to be much, much more expensive and difficult. And our capacity to do stuff is going to decrease as we suffer from the consequences - e.g. population reduction, conflicts, etc.

wolfgke 7y ago
> And our capacity to do stuff is going to decrease as we suffer from the consequences - e.g. population reduction, conflicts, etc. If the population reduces, the emission of greenhouse gases decrease which helps to reverse the effect of climate change.
- PeterisP 7y ago
  These feedback loops are in total larger than our emissions, so once we hit them in the coming decades, the global warming would continue increasing for at least a few centuries even if all humans would be dead and make zero emissions. Hitting zero emissions now (which IMHO is unrealistic) would stop global warming at something like +2C level. Hitting zero emissions in 2050 will still mean a runaway global warming, and fixing that would require some effects that go way beyond zero emissions e.g. large scale carbon sequestration (effectively negative emissions), geoengineering sci-fi or something like that. In 1980 it would have been sufficient to "just" reduce the growth.

sleepysysadmin 7y ago

You will find that predictions of climate change have been 100% false. Nobody has a crystal ball and nobody can predict what will happen in the future. So lets look into the past. https://en.wikipedia.org/wiki/Geologic_temperature_record#/media/File:All_palaeotemps.svg https://en.wikipedia.org/wiki/Geologic_temperature_record#/m... About 20,000 years ago the earth was 10 celcius colder. For the last 20,000 years the earth has been warming pretty steadily. About 100,000 years ago the world was 5celcius warmer than today. If you look at the black/red dots from the IPCC predictions. All of those have already been disproven as false and not going to happen. Overall on the graph what's happening is that we are more or less exactly flat. However look at those spikes: https://en.wikipedia.org/wiki/Eemian#/media/File:EPICA_delta_D_plot.svg https://en.wikipedia.org/wiki/Eemian#/media/File:EPICA_delta... Temperature on earth frequently rapidly spiked up in temperature. So what happened to life on earth when it was 5+ celcius warmer? It was fantastic for life. Frozen wastelands like Canada and Russia thawed and became extremely livable. People moved into these northern places. https://en.wikipedia.org/wiki/Eocene https://en.wikipedia.org/wiki/Eocene The Eocene 50 million years ago was 14celcius warmer and life thrived better than no other time in history.

gjm11 7y ago
> predictions of climate change have been 100% false That statement is itself 100% false, so far as I can tell. Here's one example. In 1982, some of Exxon's scientists wrote a memo for their management containing a graph (figure 3, page 7, of http://www.climatefiles.com/exxonmobil/1982-memo-to-exxon-management-about-co2-greenhouse-effect/ http://www.climatefiles.com/exxonmobil/1982-memo-to-exxon-ma...) saying that by 2020 CO2 levels would be in roughly the range 400..430 ppm and global mean temperature would be up by roughly 1..1.3 degrees C compared to 1960. Here we are in 2020 and the figures are about 410ppm and +0.9 degrees C. That matches up pretty well, wouldn't you say? > For the last 20,2000 years the earth has been warming pretty steadily What the graph you yourself linked to shows is something very different. There are wild oscillations in the Pleistocene (i.e., before 20k years ago), ending up with temperatures much colder than the present. Then a rapid increase from 20k to 10k years ago. Then near-flat temperatures for the last 10k years. And -- though it's over so short a period that it's hard to see on that graph -- an extremely rapid increase over the last ~50 years. > All of those have already been disproven as false and not going to happen How? By whom? > we are more or less exactly flat This https://climate.nasa.gov/vital-signs/global-temperature/ https://climate.nasa.gov/vital-signs/global-temperature/ is not what I would call "more or less exactly flat". > look at those spikes ... frequently rapidly spiked up in temperature You're looking at a portion of the Pleistocene, also known as the last Ice Age. Glaciers came and went, and the Eemian "spike" is one of those periods in which the glaciers melted. So, yes, indeed, temperatures "spiked up" and we had a transition from a large fraction of the earth's land area being covered in ice to hardly any of it being. Are you suggesting that we shouldn't be worried about climate change because the consequences might not be any more severe than those of the melting of an ice sheet covering the whole of Canada? > it was fantastic for life Pretty good for life overall, yes, and the climate change we're causing might be too. However, my own interests are parochial enough that I care much more what happens to our species and the others that we've grown to depend on, which is any entirely different question. For instance ... > The Eocene 50 million years ago was 14 celsius warmer and life thrived ... 50M years ago, sea levels were something like 100m higher than they are now. There's a handy tool at http://www.floodmap.net/ http://www.floodmap.net/ that lets you explore the consequences of a given increase in sea level (though it's a bit glitchy and it looks like maybe it doesn't have data for anything too far from the equator). At 100m, things we would lose include: about half of England and Ireland; all of the Netherlands; half of Belgium; most of western France; all of Senegal, the Gambia, and Guinea-Bissau; huge amounts of the eastern USA including more or less all of Florida, Louisiana, Delaware and Rhode Island. I'm sure life would thrive. The human race would adapt too, no doubt; we're a very adaptable species. But a whole lot of us would have our homes under water, and large regions of what's now the inhabitable world would become inhospitable to human life. E.g., a temperature rise of 14 degrees C turns San Francisco into Death Valley.