In much of the Western US (where I grew up), drought is by far the most important threat from climate change. Wars over water rights have been raging since the Los Angeles Aqueduct was built in the 1920s to bring water from the eastern slope of the Sierra Nevada to Los Angeles, drying up Owens Lake and producing toxic dust storms. In addition to precipitation droughts and soil moisture droughts and hydraulic droughts, we likely have "WATER-USE DROUGHTS". Water-use may be the biggest cause of drought, especially if increasing transpiration with temperature is being poorly modeled. Your information (in #13) about the current "greening" of the planet and the "greener" Pliocene Warm Period raised serious doubts in my mind that warmer must be drier. I'd like to know more about the models used to quantify soil moisture droughts and the data that shows increasing water vapor deficits.
Anecdotal stories say that rivers that formerly flowed year-round in Northern China apparently no longer reach the ocean much of the year due to water usage. Lakes Mead and Powell (reservoirs) on the Colorado are at record lows - fundamentally because water has been released from them feed the Colorado River Aquaducts (LA, San Diego and the Imperial Valley) and the Central Arizona Project. Yes, these reservoirs are also falling because inflow from the Upper Colorado Basin has not matches these outflows, but water from the Upper Basin is also used to supply areas outside the Upper Basin (Denver, Colorado Springs , Albuquerque, Salt Lake City, and Cheyenne). Phoenix is the fastest growing city in the US (now fifth largest) and the population in the Colorado Basin has more than doubled since 1985. Does the IPCC distinguish between drought associated with climate change and water-use?
Have to do the predictive modeling of climate dipoles such as ENSO before you try any attribution studies, as the natural variance is too great to easily discriminate the AGW portion.
Pukite: I like to use the term "unforced variability" tor the "natural variability" in climate you are talking about. (This distinguished it from the changes that have been anthropogenically "forced" by rising GHGs and aerosols.) In the Colorado River Basin, which has attracted my interest, scientists have "reconstructed" past droughts and wet periods via tree ring widths (TRWs) of species whose growth is believed to be limited by the availability of water. By comparing the change in these growth rings with change in precipitation and estimates of drought over the last century, we can look back back about a millennium and determine how much more severe and long droughts have been in this century than in the past. On that basis, the current drought as of 2021 is estimated to be as bad as any in the past millennium. (If too many other factors (noise) influence TRW, then reconstructions will underestimate past unforced variability. You can find some obsolete information in a comment I wrote last year and the latest paper below, though this wet winter probably will change everything. Perhaps droughts are really climate change until they have lasted for the traditional minimum of 30 years.
Here's "Drought under global warming: a review", Aiguo Dai 2011:
"For example, successive ‘‘megadroughts’’, unprecedented in persistence (20–40 year) yet similar in severity and spatial distribution to the major droughts experienced in modern-day’s North America, occurred during a 400-year-long period in the early to middle part of the second millennium AD over western North America. Compared with these multi-decadal droughts, the modern-day droughts in the 1930s and 1950s had similar intensity but shorter durations.."
If you look for the paper on scholar.google.com you can see figure 1 which some very extended droughts long in the past.
Steve: Thanks for the reply. Yes, papers published a decade ago talked about a megadroughts centuries ago in the American Southwest. Some native American societies there suffered huge setbacks. A few years ago, papers were talking about the current drought being ONE of the five or six most severe droughts in the past millennia. In a paper published in 2022, 2021 was making history (though not yet in terms of duration):
Rapid intensification of the emerging southwestern North American megadrought in 2020–2021
Abstract: A previous reconstruction back to 800 ce indicated that the 2000–2018 soil moisture deficit in southwestern North America was exceeded during one megadrought in the late-1500s. Here, we show that after exceptional drought severity in 2021, ~19% of which is attributable to anthropogenic climate trends, 2000–2021 was the driest 22-yr period since at least 800. This drought will very likely persist through 2022, matching the duration of the late-1500s megadrought.
If this were how much 1 degC of global warming has enhanced drought, it is disturbing to imagine what 2 degC (mid-century) and 3 degC (likely end-of-century) will be like.
Frank used the term "unforced variability" , which is misguided and wrong. There is no such thing as unforced variability as objects don't suddenly start moving n their own.
The atmosphere and ocean are always in motion (somewhere). Lorentz discovered that the motion of fluids and other non-linear physical systems is determined by the laws of physics, but unpredictable, because the future is excessively sensitive to the system's initial state. Lorenz discovered this when exploring a system of equations that had some aspects of a model that predicts weather. When a computer crashed in the middle of a run, Lorentz went back and input the calculated conditions an hour or two earlier in the run, after truncating five places to the right of the decimal point. He found that his original and new calculations diverged quickly. We can never know the initial state of the weather or climate with enough precision enough to accurately predict the future. Lorenz called this DETERMINISTIC CHAOS: "When the present determines the future, but the approximate present does not approximately determine the future.
Weather prediction models are initialized with currently measured conditions from around the world (temperature, wind and direction, humidity, time of day) and then allowed to evolve over times according to the laws of physics (with some help for phenomena like clouds and precipitation). The model can forecast the state of the weather a week or two in the future. If you were to randomly adjust the initial temperatures up or down by 0.01 degC (and they aren't measured this accurately), the forecast may be very different in a week and begins to lack any skill at predicting weather disappears between 1 and 2 weeks. In the case of climate models, scientists usually don't even try to ia defined set of starting conditions.
Two months ago, no one would have been able to predict whether we will have El Nino conditions next winter with an increased likelihood of rain in the American Southwest. In two months, unusual winds blowing east toward South American will or won't stabilize and produce an El Nino that will strengthener the next six months. EL Ninos and La Ninas are chaotic, they can't be predicted a year or more in the future. Everything about weather and climate is unpredictable in the long run - that is chaos or "forced variability" or "internal variability"
That's what they have lead you to believe. Why aren't ocean tides chaotic? Please explain that and then consider what happens to subsurface tides along the equatorial thermocline where the interface is most clearly delineated.
At his old blog, our host has an 8 part series on chaos, like this 13 part series on extreme weather. I should simply refer you to this great resource and not risk making any mistakes, but I'll offer some pointers below
The regular pattern of tides is "externally forced", driven by the gravitational force from the moon and tides. The higher tides that come with strong winds and especially hurricanes are chaotic, because their driving forces are chaotic. The waves on the surface of the ocean are also driven by winds which are also chaotic. Both tides and waves dwarf sea level rise (currently about 1 inch/decade) driven mostly by expansion of water with warming of the ocean and melting of ice caps.
Solutions to the Navier-Stokes equations for fluid flow are chaotic. The atmosphere and ocean are fluids. Above a certain Reynolds number, fluid flow is turbulent. The distances fluids flow on Earth guarantee their flow will be turbulent.
Professionals working with chaos use the term internal variability for the chaotic systems and "external" for outside factors that produce change. In climate science, we talk about climate change that is "forced" by man (anthropogenic) through rising GHGs, aerosols and land use as opposed to "natural variability" in climate, which dwarfs forced change on time scales of less than a decade. The problem is the term "natural" also refers to changes in the sun and volcanos that also force climate change. On an even longer time scale, Milankovitch's changes in the Earth's orbit around the sun are another natural and enormous external forcing that effects climate. Using the term unforced variability or internal variability clarifies that a change is attributable to chaos, but many use the ambiguous term "natural variability".
Weather prediction models and climate models break the atmosphere up into grid cells and apply the laws of physics to the flow of each grid cell. At the link below, you can see the ocean currents and eddies produced by the highest resolution models we have the computing power to run. However, inside each one of these grid cells, the flow is also chaotic and full of eddies. And if the models were initialized with slightly different starting conditions, the chaotic nature of fluid flow means these simulated eddies would soon be completely. In the atmosphere, grid cell that are roughly 100x100 km contain none of the details of the turbulent mixing that occurs as individual thunderstorms rise more than 10 km to the tropopause in the intertropical convergence zone.
Here's an extract from p.1572 on hydrological droughts:
"Drivers of streamflow and surface water deficits are complex and strongly depend on the hydrological system analysed..
.. In addition, the assessment of groundwater deficits is very difficult given the complexity of processes that involve natural and human-driven feedbacks and interactions with the climate system. Streamflow and surface water deficits are affected by land cover, groundwater and soil characteristics, as well as human activities (water management and demand, damming) and land-use changes."
I removed the references to make it more readable.
In much of the Western US (where I grew up), drought is by far the most important threat from climate change. Wars over water rights have been raging since the Los Angeles Aqueduct was built in the 1920s to bring water from the eastern slope of the Sierra Nevada to Los Angeles, drying up Owens Lake and producing toxic dust storms. In addition to precipitation droughts and soil moisture droughts and hydraulic droughts, we likely have "WATER-USE DROUGHTS". Water-use may be the biggest cause of drought, especially if increasing transpiration with temperature is being poorly modeled. Your information (in #13) about the current "greening" of the planet and the "greener" Pliocene Warm Period raised serious doubts in my mind that warmer must be drier. I'd like to know more about the models used to quantify soil moisture droughts and the data that shows increasing water vapor deficits.
Anecdotal stories say that rivers that formerly flowed year-round in Northern China apparently no longer reach the ocean much of the year due to water usage. Lakes Mead and Powell (reservoirs) on the Colorado are at record lows - fundamentally because water has been released from them feed the Colorado River Aquaducts (LA, San Diego and the Imperial Valley) and the Central Arizona Project. Yes, these reservoirs are also falling because inflow from the Upper Colorado Basin has not matches these outflows, but water from the Upper Basin is also used to supply areas outside the Upper Basin (Denver, Colorado Springs , Albuquerque, Salt Lake City, and Cheyenne). Phoenix is the fastest growing city in the US (now fifth largest) and the population in the Colorado Basin has more than doubled since 1985. Does the IPCC distinguish between drought associated with climate change and water-use?
Have to do the predictive modeling of climate dipoles such as ENSO before you try any attribution studies, as the natural variance is too great to easily discriminate the AGW portion.
Pukite: I like to use the term "unforced variability" tor the "natural variability" in climate you are talking about. (This distinguished it from the changes that have been anthropogenically "forced" by rising GHGs and aerosols.) In the Colorado River Basin, which has attracted my interest, scientists have "reconstructed" past droughts and wet periods via tree ring widths (TRWs) of species whose growth is believed to be limited by the availability of water. By comparing the change in these growth rings with change in precipitation and estimates of drought over the last century, we can look back back about a millennium and determine how much more severe and long droughts have been in this century than in the past. On that basis, the current drought as of 2021 is estimated to be as bad as any in the past millennium. (If too many other factors (noise) influence TRW, then reconstructions will underestimate past unforced variability. You can find some obsolete information in a comment I wrote last year and the latest paper below, though this wet winter probably will change everything. Perhaps droughts are really climate change until they have lasted for the traditional minimum of 30 years.
https://scienceofdoom.com/2020/06/07/models-and-rainfall-vii-australia-canesm2-csiro-miroc-and-mri-rcp4-5-rcp8-5/#comment-172016
https://escholarship.org/content/qt6sm1c6hf/qt6sm1c6hf.pdf
Here's "Drought under global warming: a review", Aiguo Dai 2011:
"For example, successive ‘‘megadroughts’’, unprecedented in persistence (20–40 year) yet similar in severity and spatial distribution to the major droughts experienced in modern-day’s North America, occurred during a 400-year-long period in the early to middle part of the second millennium AD over western North America. Compared with these multi-decadal droughts, the modern-day droughts in the 1930s and 1950s had similar intensity but shorter durations.."
If you look for the paper on scholar.google.com you can see figure 1 which some very extended droughts long in the past.
Steve: Thanks for the reply. Yes, papers published a decade ago talked about a megadroughts centuries ago in the American Southwest. Some native American societies there suffered huge setbacks. A few years ago, papers were talking about the current drought being ONE of the five or six most severe droughts in the past millennia. In a paper published in 2022, 2021 was making history (though not yet in terms of duration):
Rapid intensification of the emerging southwestern North American megadrought in 2020–2021
Abstract: A previous reconstruction back to 800 ce indicated that the 2000–2018 soil moisture deficit in southwestern North America was exceeded during one megadrought in the late-1500s. Here, we show that after exceptional drought severity in 2021, ~19% of which is attributable to anthropogenic climate trends, 2000–2021 was the driest 22-yr period since at least 800. This drought will very likely persist through 2022, matching the duration of the late-1500s megadrought.
https://escholarship.org/content/qt6sm1c6hf/qt6sm1c6hf.pdf
If this were how much 1 degC of global warming has enhanced drought, it is disturbing to imagine what 2 degC (mid-century) and 3 degC (likely end-of-century) will be like.
Frank used the term "unforced variability" , which is misguided and wrong. There is no such thing as unforced variability as objects don't suddenly start moving n their own.
Suggest you read up on climate variability such as ENSO. Modeling that elsewhere but I also have an article here on SubStack called SubSurface.
The atmosphere and ocean are always in motion (somewhere). Lorentz discovered that the motion of fluids and other non-linear physical systems is determined by the laws of physics, but unpredictable, because the future is excessively sensitive to the system's initial state. Lorenz discovered this when exploring a system of equations that had some aspects of a model that predicts weather. When a computer crashed in the middle of a run, Lorentz went back and input the calculated conditions an hour or two earlier in the run, after truncating five places to the right of the decimal point. He found that his original and new calculations diverged quickly. We can never know the initial state of the weather or climate with enough precision enough to accurately predict the future. Lorenz called this DETERMINISTIC CHAOS: "When the present determines the future, but the approximate present does not approximately determine the future.
Weather prediction models are initialized with currently measured conditions from around the world (temperature, wind and direction, humidity, time of day) and then allowed to evolve over times according to the laws of physics (with some help for phenomena like clouds and precipitation). The model can forecast the state of the weather a week or two in the future. If you were to randomly adjust the initial temperatures up or down by 0.01 degC (and they aren't measured this accurately), the forecast may be very different in a week and begins to lack any skill at predicting weather disappears between 1 and 2 weeks. In the case of climate models, scientists usually don't even try to ia defined set of starting conditions.
Two months ago, no one would have been able to predict whether we will have El Nino conditions next winter with an increased likelihood of rain in the American Southwest. In two months, unusual winds blowing east toward South American will or won't stabilize and produce an El Nino that will strengthener the next six months. EL Ninos and La Ninas are chaotic, they can't be predicted a year or more in the future. Everything about weather and climate is unpredictable in the long run - that is chaos or "forced variability" or "internal variability"
https://en.wikipedia.org/wiki/Chaos_theory
That's what they have lead you to believe. Why aren't ocean tides chaotic? Please explain that and then consider what happens to subsurface tides along the equatorial thermocline where the interface is most clearly delineated.
At his old blog, our host has an 8 part series on chaos, like this 13 part series on extreme weather. I should simply refer you to this great resource and not risk making any mistakes, but I'll offer some pointers below
https://scienceofdoom.com/roadmap/natural-variability-and-chaos/
The regular pattern of tides is "externally forced", driven by the gravitational force from the moon and tides. The higher tides that come with strong winds and especially hurricanes are chaotic, because their driving forces are chaotic. The waves on the surface of the ocean are also driven by winds which are also chaotic. Both tides and waves dwarf sea level rise (currently about 1 inch/decade) driven mostly by expansion of water with warming of the ocean and melting of ice caps.
Solutions to the Navier-Stokes equations for fluid flow are chaotic. The atmosphere and ocean are fluids. Above a certain Reynolds number, fluid flow is turbulent. The distances fluids flow on Earth guarantee their flow will be turbulent.
Professionals working with chaos use the term internal variability for the chaotic systems and "external" for outside factors that produce change. In climate science, we talk about climate change that is "forced" by man (anthropogenic) through rising GHGs, aerosols and land use as opposed to "natural variability" in climate, which dwarfs forced change on time scales of less than a decade. The problem is the term "natural" also refers to changes in the sun and volcanos that also force climate change. On an even longer time scale, Milankovitch's changes in the Earth's orbit around the sun are another natural and enormous external forcing that effects climate. Using the term unforced variability or internal variability clarifies that a change is attributable to chaos, but many use the ambiguous term "natural variability".
Weather prediction models and climate models break the atmosphere up into grid cells and apply the laws of physics to the flow of each grid cell. At the link below, you can see the ocean currents and eddies produced by the highest resolution models we have the computing power to run. However, inside each one of these grid cells, the flow is also chaotic and full of eddies. And if the models were initialized with slightly different starting conditions, the chaotic nature of fluid flow means these simulated eddies would soon be completely. In the atmosphere, grid cell that are roughly 100x100 km contain none of the details of the turbulent mixing that occurs as individual thunderstorms rise more than 10 km to the tropopause in the intertropical convergence zone.
https://www.gfdl.noaa.gov/html5-video/?width=940&height=530&vid=cm26_v5_sst&title=
Frank,
Here's an extract from p.1572 on hydrological droughts:
"Drivers of streamflow and surface water deficits are complex and strongly depend on the hydrological system analysed..
.. In addition, the assessment of groundwater deficits is very difficult given the complexity of processes that involve natural and human-driven feedbacks and interactions with the climate system. Streamflow and surface water deficits are affected by land cover, groundwater and soil characteristics, as well as human activities (water management and demand, damming) and land-use changes."
I removed the references to make it more readable.