365 Days of Climate Awareness 328: IPCC AR6, Volume 2: Impacts, Adaptation and Vulnerability

We’re nearing the end of this 365 Days series, with a little more than a month—thirty-seven days’—of posts left. (And of course I realize the series could go on indefinitely, as the work to mitigate and adapt to climate change is only beginning.) But it will be time for me to redirect my time elsewhere, though I’ll continue writing. Just not in a daily, compact format like this.

Climate change studies by region. Does the west win a prize?

But the time has come to take all of the basics, and not-so-basics, of climate science, and the general global knowledge we’ve gathered throughout these 327 posts, and bring them to fruition by going in some detail through the current AR6 report. Volume 1, the Physical Science Basis, has much in common with the several hundred posts I’ve made already. So here I’ll move on to Volume 2, and address the impacts of global warming on some of the natural systems around the world.

Different baselines for global temperature anomalies. In science, measurements are a function of the reference point.

This is only an introduction, and if you have sincere interest—as I hope you do—there is a link to the report at the bottom. It’s not easy reading, I won’t sugarcoat that, and the report, like Volume I last year, is only in draft form, so I’m really not supposed to be linking to it or reproducing any graphs. But as before, I think climate change is too important to keep worthwhile information back. Like with my hopscotch tour of the planet, I will survey the chapters of Volumes 2 and, later, 3 (Adaptation and Mitigation), to give you a fair sampling of what this massive collaborative effort has to offer.

Global impacts of various changes in climate through the eons. (Note that the planet has been in icehouse conditions since the Paleogene, and the current spike in temperature is still well below earlier geological ages--when the planet lookd far different.)

Knowledge is not enough. This is not an academic exercise. It’s good to learn more about our natural systems, so we can better understand how to coexist within them and how they are changing. But the goal isn’t to talk about climate change, it’s to act on it, so our society doesn’t fail. Career climate researchers never leave, or never stray far, from the cycle of testing, discovery and analysis. Because of them we’ve learned what we know now. But the urgency of global warming will not be met in the laboratory. It will be met worldwide, everywhere—or not.

Temperature changes during this interglacial period, and recent human impacts.

Tomorrow: AR6 V2 Ch2: Terrestrial and freshwater ecosystems.

Be brave, be steadfast, and be well.

IPCC 6th Assessment Report, Volume 2: Impacts, Adaptation and Vulnerability

365 Days of Climate Awareness 327 – The IPCC’s AR6 predictions

Over the past 12 months the Intergovernmental Panel on Climate Change (IPCC), the UN climate change research office, has in stages released its Sixth Assessment Report (AR6) on global climate. The report is broken down into three volumes: (1) The Physical Science Basis; (2) Vulnerabilities and Impacts; and (3) Adaptation and Mitigation. A fourth report, the synthesis of all three volumes, will be complete in late 2022 or early 2023.

Temperature changes between glacial and interglacial periods.

IPCC AR6 global temperature model to 2100.

Thousands of scientists with many different research specialties—marine biology, ocean physics, glacial science, atmospheric sciences, to name a very few—collaborate on collating data and writing the report. Large teams collaborate on each chapter, which are then edited and set within the larger volume, itself part of the comprehensive Assessment Report. The six reports have spanned the last thirty-plus years since the IPCC’s founding in 1988: 1990-92 (AR1); 1995 (AR2); 2001 (AR3); 2007 (AR4); 2015(AR5); 2022 (AR6). The reports have grown in length, scope, and urgency with each cycle.

IPCC AR6 global CO₂ and temperature change models to 2100.

IPCC AR6 global models for temperature, precipitation, September Arctic sea ice extent and mean sea level to 2100.

The latest, AR6, states in the strongest and most unequivocal terms yet that humans are responsible for the rapid planetary warming of the past century-plus, and that large changes in the global climate regime are inevitable without large and immediate reductions in greenhouse gas emissions.  Since the last glacial maximum until now, the world has warmed roughly 5°C/9°F. Some temperature rise scenarios show global increases of that within the next eighty years, with sea level rise of 0.75 m/2.5 ft, enough to impact coastal cities and homes around the world, with some in real danger of being lost. 

NOAA coastal flooding visualization tool

IPCC AR6 September Arctic sea ice extent model to 2100.

IPCC AR6 ocean surface pH model to 2100.

The combination of these factors and more: higher temperatures, winters diminishing, shoulder seasons (spring/fall) being compressed into what used to be winter; greater and more violent precipitation; dramatically warming and acidifying oceans; loss of ice around the world; in some cases amplify each other in vulnerable zones such as coasts and low-elevation areas like river basins. Eustatic (global) sea level rise will also affect river levels and their local and regional ecosystems. System response to the complicated effects of global warming will be likewise complex and far-reaching.

Tomorrow: IPCC AR6 Vulnerabilities and Impacts.

Be brave, be steadfast, and be well.

365 Days of Climate Awareness 326 – Hindcasting

One of the most powerful tools we have for testing and tuning climate models is “hindcasting”, where the model is run over a historical period, usually decades long. The starting, intermediate and end conditions are already known, so the model’s results can be compared statistically to the historical data. A small side benefit of this method is that, when the model is found to give historically robust results, the model itself can be used to provide insights about parts of the globe which have been inadequately monitored through the years.

Tidal level model hindcasting.

Accuracy through a prior range in time is not a guarantee of accuracy into the future. Predictions are hard! And conditions, such as greenhouse gas inputs, change. We are limited by the relatively recent development of our climate monitoring capabilities, and the immediacy of the impacts of global warming. We don’t have a long timespan of direct measurements, or a leisurely run of decades to come in which to build our base of knowledge. Climate is changing, now, with increasing speed.

NASA verification of global temperature model average against actual.

For its imperfection, hindcasting is still a primary tool of climate modelers. Increasing computer speed and more detailed information about conditions in the atmosphere, ocean and the rest of the biosphere provide the means for modelers to make more comprehensive, higher-resolution models. The more variables around the globe which can be controlled for, from basics like temperature, humidity and albedo, to more advanced types such as evapotranspiration rates and oceanic gas and heat fluxes, the more robust the model will be.

1)     El Niño/Southern Oscillation (ENSO) hindcasting. Rather more complicated than water level at a single tidal station!

This is why predictive climate model runs normally include a hindcasting run-up of several decades, to establish that any given model run is as true to known data as we can make it. It’s a regular, common-sense verification like any equipment safety checklist.

Tomorrow: model results from the IPCC’s Sixth Assessment Report (AR6).

Be brave, be steadfast, and be well.

365 Days of Climate Awareness 325 – Running the Climate Model

Whether the model covers the entire globe, or only a portion of it, the area of interest is divided into a spatial grid, not only horizontally but vertically, incorporating ocean depths and the upper atmosphere. At “time zero” (t₀ or t_init), the baseline from which the climate model begins running, the boundary conditions and the world’s initial temperature values are called “primary conditions”. This name simply refers to the state of the system—the values of all the system variables, including temperature—at the outset of the model run.

Lateral and vertical model gridding, over both land and sea.

Climate models’ final output is generally a gridded (mapped) set of predicted temperatures around the globe: one complete map for each time step, from beginning (t₀/t_init) to end (t_n, or t_final). At the end of each time step, once the map has been completed, the updated temperatures across the entire map grid are loaded back into the equations along with the preset boundary conditions for the next time step, and the model is run again. This process continues, through each time step, until the finish time (January 1, 2100, or otherwise) is reached. And that concludes one run of the model.

Improvements in grid resolution over the years.

There are dozens of models around the world, some focusing on the atmosphere, some on the oceans, some on the atmosphere, some including societal and economic components. Part of the role of the Intergovernmental Panel on Climate Change (IPCC) is to evaluate the different models and integrate their results into one comprehensive set of predictions for the periodic Climate Assessment. The present assessment is #6 (AR6) and is now available online in final draft.

Results of a one hundred-year difference model.

Tomorrow: hindcasting.

Be brave, be steadfast and be well.

365 Days of Climate Awareness 324 – W. Virginia v. the EPA

Is this how our republic dies, at the hands of six supremely unqualified sophists? Their recent opinions are judicial masturbations with no pretense of consistency beyond might-makes-right. Alternately ignoring the text of the Constitution—Amendment 9, in the Obergefell abortion case—or inventing arbitrary distinctions within it—the “Major Questions Doctrine” of the W. Virginia case—they are shaping law by any convenient means toward their premeditated goals. While the verdict in W. Virginia is not, to my mind, quite the death knell for society it’s portrayed as, it is a gunshot to the stomach, one that will lead slowly and painfully to death if not treated right away.

 At issue is the Clean Power Plan proposed by the Obama administration in 2015, to lower carbon emissions for electricity generation by 32% from 2005 levels by 2030. For its authority, the administration classified carbon dioxide as a pollutant subject to regulation under the Clean Air Act. 28 states opposed the plan and many went to court. There were three lines of attack: (1) there remain unreconciled differences between the House and Senate bills which were signed into law, leaving room for interpretation on the EPA’s jurisdiction over carbon dioxide; (2) the CPP authorized states to act on classes of power plants, not individual power plants as before—i.e., the CPP gave states governments too much power; (3) that under the 10^th Amendment, the EPA lacks the power to delegate that much authority to states.

West Virginia along with nineteen other states challenged a 2021 appellate court’s decision in favor of the rule. The EPA then moved to declare the suit moot on the premise that the Clean Power Plan had been shelved. But the Roberts court agreed to hear it, on the premise that future climate action by the EPA was too likely to ignore. On June 30, 2022 the Roberts court issued its opinion, based on a never-before-named “Major Questions Doctrine”.

The line of thinking has existed for some time, and has been applied in several cases through the decades, limiting federal agencies from overly broad interpretations of vaguely-worded laws. In employing this new doctrine, the Supreme Court shied away from what many feared was at stake, Congress’ right to delegate any regulatory authority whatsoever (which would have rendered all federal agencies in the Executive branch illegal). Previous applications of the principle—not yet elevated to the status of constitutional “doctrine”—include preventing federal drug laws from being applied to drug-assisted medical suicide. While previous Courts have ruled against executive agencies aggressively interpreting environmental laws, the Major Questions Doctrine is so dangerous because there is no clear standard for its application.

At issue is whether an executive agency can be guided by changes in conditions and in the state of knowledge, or whether there is some boundary—presumably between “minor” and “major” questions—at which Congress must intervene. The science of global warming, notwithstanding ExxonMobil’s and the rest of the oil industry’s concerted disinformation campaigns—has been established for over thirty years.

The Roberts decision invalidates the CPP, holding that Congress must re-delegate specific authority on greenhouse gas emissions to the EPA. With this ruling the Roberts court has taken away all power of the EPA to take any action on carbon dioxide or other greenhouse gas emissions, except as they are accidentally included by name in the law already. Given Republican obstruction of Congress, that remains impossible in the near future. Combined with their other decisions on voting rights and other issues, it summons the specter of no action ever being taken at the federal level on climate change.

You can be sure that that the “Major Questions Doctrine” was very thoroughly prepared within the Heritage Foundation before being passed along to and advanced by this court, as the easiest line of attack on environmental and other forms of regulation. More suits citing it are without doubt already being drawn up. By focusing on dubious legalistic hair-splitting, and treating the larger issue with ignorance and contempt, the Roberts court has once again acted decisively on behalf of corporate interests over the welfare of the United States, its citizens, and the world.

Tomorrow: running a climate model.

Be brave, be steadfast, and be well.

365 Days of Climate Awareness 323 –Boundary Conditions: Emissions Scenarios

Boundary conditions are mathematical expressions of the limits and inputs of a system. The many and complicated sets of equations—enough to fill 18,000 printed pages--which compose general circulation models (GCMs) require these boundary conditions to even run. Without them, there isn’t enough information for a computer to obtain results. And if these boundary conditions are unrealistic, the model will go off the rails and give wildly bad results. These boundary conditions tend to be empirical, that is, based on observations. However, a number are themselves derived from models, making them semi-empirical. But for climate modeling, foremost among the boundary conditions are emissions scenarios.

There are several very important sets of boundary conditions. These include:

•           Topography (treated as constant)
•            Ocean bathymetry (treated as constant)
•            Incoming solar radiation (varies with time)
•           Land-use scenarios (change over time)
•           Emissions scenarios (change over time)

IPCC Carbon pathways.

The last two themselves are the results of two sets of complex projections. One is called “Shared Socioeconomic Pathways” (SSPs). These pathways represent varying levels of international cooperation and technological progress:

•         Population trends
•          Economic activity
•          Technological development
•          Political and social will for change

The five SSPs are:

• .      SSP1: sustainable pathway. Global commons ar preserved, limits of nature are respected.
• .      SSP2: medium pathway. Limited cooperation between states. Global population growth is moderate and environmental systems degrade.
• .      SSP3: Regional rivalry. Nationalism and regional conflicts push global issues into the background.
• .      SSP4: Inequality. Contrast between globally cooperating societies and those stalling is widening. Environmental policies address local problems in some regions, but not in others.
• .      SSP5: Fossil-fueled Development. Innovations, technological progress and an energy-intensive lifestyle worldwide based on increased use of fossil fuels.

The second set of projections are called “Representative Carbon Pathways” (RCPs), and these represent different climatic scenarios with various levels of radiative forcings (global heat gain, post #91). They are stated as temperature gains over 1750 average, and range from 1.9°C/3.4°F to 8.5°C/15.3°F. Treating these two broad topics—socioeconomic factors and environmental impacts—separately produced a wide range of possible global warming scenarios. In the climate models, both SSPs and RCPs are boundary conditions which help determine the state of the world climate by 2100.

Tomorrow: West Virginia v. the EPA.

Be brave, be steadfast, and be well.

365 Days of Climate Awareness 322 – General circulation models 3: boundary conditions

I’ll admit that the term “boundary conditions” used to make me twitch. Partial differential equations and 4-dimensional (three physical dimensions plus time) calculus were always difficult hurdles for me (and not a small part of the reason why I moved from physics over to geology!) But differential equations—diffEQ’s, as they’re known in the biz—are the real mathematic sorcery within climate, or almost any natural system model. In the end, you plug numbers into the many different variables and receive numerical output. You can look at all math as just increasingly fancy types of addition and subtraction. But what makes an equation “differential” is that it focuses on differences.

A sine wave, broken into a series of discrete measurements. 

This is because a “differential” in mathematics is computed from a rate of change. How much does one variable (y, for example) change when another (x) changes? This rate of change itself can vary: an increase in (x) of 1 might under different circumstances produce different changes in (y). Look at the sine wave, a smoothly varying curve, in the illustration. With each identical forward step in the horizontal axis (x), the height (y) changes by a slightly different amount from the previous, and following, amounts. That’s what creates the curve, as opposed to a straight line. In a curve, the rate of change—the slope of the graph—changes as you move along it. That’s bad enough. How about more variables? What if (y) depends not only on (x), but also on (z), (a) and (b)? Hence the sorcery!

Ye olde diffEQ. The differential proper: dy ("change in y") over ("with respect to") dx ("change in x"). Not a constant! Change in the differential's value is the heart of mathematical modeling.

In nature, where just about nothing is constant (though we often pretend they are, to simplify the math), rates of change are the simplest means to approach almost any topic. Predicting the water level and current velocity of tides—extremely important for shipping—are an ideal application of diffEQ’s. Disease control, where microbes grow exponentially—with increasing speed as their population grows, until the system becomes full—is another. For a climate example, the temperature of ocean water will vary in space—east (x), north (y), depth (z), and in time (t). Those four fundamental variables determine quite a lot, but not everything!

Exponential increase in global COVID cases, early 2020.

But nature also has limits. COVID did not continue to spread unchecked, because earth’s population is finite, and the spread rate decreased, and (much) later the actual case load began to decrease. A cycle like the tides has inherent limits within itself—the regular motion of earth and moon—but their height and flow rates are also constrained by things such as the local bathymetry, which limit how much water can pass through. These natural limits, whether based on population, physical barriers like mountains or coastlines, or physical properties like wind speed or incoming solar radiation, are called boundary conditions.

Measurements of tidal height (red) and current (blue) for the St. John's River in Jacksonville, FL Note that the curves are slightly out of phase. The cycle of tidal height lags slightly behind the cycle of current speed.

A more complex species of diffEQ’s contains these built-in boundaries, so the system and its variables don’t become unrealistic. This is because climate models are relentlessly tuned to known, measured aspects of global climate. In climate models, most boundary conditions are empirical: that is, based on measurements, not theoretical derivations. Topography (mountains, valleys, plains.) and bathymetry (coastlines, channels and basins) are two obvious, measured boundary conditions. Other empirical boundary conditions include the amount of solar energy entering earth’s climate system (not constant! Because earth is in motion, and its orbit is elliptical), changing land use patterns (a very important aspect), and many more. These models are complicated.

Tomorrow: some of the main boundary conditions used in IPCC climate models.

Be brave, be steadfast, and be well.