A Quick Primer on Climate Change

One: Introduction

We are living in the midst of an unfolding climate crisis. At this point, we are well past debating whether or not the earth’s climate is changing, whether or not human activities are the primary cause, and whether or not these issues merit our attention.

We are experiencing a rapid acceleration of climate impacts. We are living with catastrophic impacts that were, until recently, predicted to take place sometime in the distant future. And predictions of future effects are growing increasingly dire.

We understand that ‘business as usual’ leads rapidly and inevitably to a planet with atmospheric conditions very different from those to which human civilization is adapted. The extinction of our species -- and half of all other species – within a few generations is a real possibility.

In order to stabilize the earth’s climate, the challenge before us is to get our emissions of planet-heating gases down to zero and to draw excess CO2 out of the atmosphere as quickly as possible. And time is not on our side.

Mike McGinn, former mayor of Seattle, said, “We are the first generation to see the effects of climate change and the last generation who can do anything about it.”

Two: the greenhouse gas layer and CO2

Let’s start with the greenhouse gas layer.

Think of the greenhouse gas layer as a heat-trapping blanket surrounding the earth. It maintains a balance between incoming and outgoing radiation. By trapping some heat within the earth’s atmosphere, it maintains conditions that are hospitable to life on earth. Without a greenhouse gas layer, the average surface temperature would be around 60 degrees Fahrenheit lower than it is at present.

Carbon dioxide, or CO2, is the main component of the earth’s greenhouse gas layer. For billions of years, the concentration of CO2 in the earth’s atmosphere has been maintained in a dynamic balance between the amount of CO2 produced (by wildfires, by volcanoes, by decomposition, and by other natural and human activities) and the amount of CO2 absorbed or sequestered (through photosynthesis and absorbed by the oceans and by the soil).

We started to rock that boat around 200 years ago, at the start of the Industrial Revolution when we started using fossil fuels: first coal, then petroleum, and then natural gas. Fossil fuels are old plants that lived millions of years ago, were transformed through geological processes, and have been conveniently stored underground.

Fossil fuels are amazingly dense, easily transportable carriers of energy. Fossil fuels are bundles of carbon-hydrogen molecules – carbohydrates! The energy content of one gallon of gasoline is equivalent to several weeks of human labor. It’s no wonder that we fossil fuels provide over 80% of the primary energy used in the United States.

But the problem is this: when we burn fossil fuels to harness their stored energy, we release CO2 into the atmosphere, thereby increasing the layer of heat-trapping greenhouse gases – and the blanket gets thicker.

And the planet gets hotter.

Three: The other greenhouse gases

CO2 is the main greenhouse gas and results mostly from the combustion of fossil fuels, from deforestation, and the burning of biomass. Around three-quarters of the greenhouse “blanket” is CO2.

But we are also releasing other heat-trapping gases into the earth’s atmosphere:

Methane, or CH4, is the main component of natural gas. Emissions result from fossil fuel production, enteric fermentation in livestock, landfills, and coal mining

Nitrous oxide, or N2O, results mainly from the use of nitrogen fertilizers in industrial agriculture. (Most of those nitrogen fertilizers are derived from natural gas).

And the fluorinated gases, or F-gases (CFC’s, HFC’s, HCFC’s, and others) which are man-made chemical compounds widely used as refrigerants, solvents, pesticides, and as electrical insulators.

These other greenhouse gases vary widely in their residence time in the atmosphere, in their “global warming potential,” which is their ability to trap outgoing radiation (a bad thing!)

Four: Paleoclimate evidence

Climate scientists look to the past, the present, and the future. Their work integrates results from backward-looking paleoclimate data, observations of current phenomena, and forward-looking computer models.

Current phenomena: global average temperature is about 1.2°C (2 degrees F) above the pre-industrial average is increasing at about 0.2°C per decade. Temperatures at the polar regions have risen at three times the global average.

Ice core data from Antarctica reveals an 800,000-year paleoclimate record:

The blue line in the graph is the concentration of CO2 in the atmosphere and the red line is average temperature. The blue scale is on the left and the red scale is on the right.

For the last 800,000 years, CO2 levels have moved up and down within a range between roughly 180 and 280 ppm. That’s the horizontal band that’s shaded in light blue. You can think of that as the Earth’s comfort zone.

Note that we are now -- on the far right side -- up above 412 parts per million, or ppm – way, way outside that comfort zone.

Prior to human interference in the climate system, these up-and-down swings, or oscillations, were largely attributable to changes in the earth’s tilt and orbit around the sun.

The troughs are the Ice Ages and the peaks are the warm interglacial periods. We see that the Earth cycled between Ice Ages and interglacial periods with each cycle lasting around 100,000 years.

As noted, the last peak is the Eemian period, the interglacial period prior to the last Major Ice Age. Average temperatures were 5 or 6 degrees C higher than today’s temperature and sea levels were 20 to 30 feet higher than present, even though CO2 levels were around 280 ppm, far lower than they are today.

The most recent trough is the last Major Ice Age. During this time, Canada and much of the northern United States were covered in ice sheets over a mile thick, sea level was hundreds of feet lower than today, and average temperatures were lower than at present.

Following the last Ice Age, around 14,000 years ago, as the Earth’s temperature increased, sea levels rose 12 to 15 feet per century for several centuries.

And, finally, note the most recent red chunk called the Holocene. It’s a 12,000-year interglacial period of unprecedented climatic stability. Temperature has been relatively stable. Sea levels have been relatively stable. And this long period of stability saw the emergence of agriculture, which allowed cities and human civilizations to develop and flourish.

We have now departed the global average temperature range of the Holocene.

We are living with CO2 levels that far exceed those during the Eemian period, the last interglacial, when sea levels were 20 to 30 feet higher than at present.

We are living with climate conditions that the Earth has not seen for over 3 million years.

Our species has never existed with these climate conditions

Five: Tipping points

In recent years we have started talking about climate tipping points.

In Stories of My Grandchildren, Dr. James Hansen says, “The urgency of the climate crisis derives from the nearness of climate tipping points, beyond which climate dynamics can cause rapid changes out of humanity’s control. Tipping points occur because of amplifying feedbacks.”

Consider the “ice-albedo effect:” increased temperatures in Arctic regions cause increased melting of sea ice which turns reflective ice into dark water, which absorbs more heat, which causes temperatures to increase even further, which causes more ice melt, and on and on in a vicious cycle.

Consider melting permafrost: as temperatures increase, permanently frozen tundra begins to melt, causing the release of both CO2 and methane, which causes additional warming, which causes additional CO2 and methane release, and on and on in another vicious cycle.

Twenty years ago, tipping points were considered likely only if global warming exceeded 5 degrees C. We now understand that we are venturing into a minefield of tipping points at warming of just over 1 degree C.

These parts of our earth are at significant risk of triggering tipping points:

• Coral reefs
• Arctic, Greenland, and Antarctic ice sheets
• Boreal forests
• Amazon Rainforest
• Permafrost, and
• Gulf Stream, or Atlantic circulation

Six: The 2015 Paris Agreement

In Paris in December of 2015, after decades of deliberation, the nations of the world finally reached an agreement on the climate crisis. The Paris Agreement had a stated objective of “…keeping a global temperature rise this century well below 2OC above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5OC.”

Even if all the nations that signed the 2015 Paris Agreement lived up to their emissions reduction pledges -- a highly unlikely outcome -- we would be living with over 3OC (5.4OF) temperature rise by the end of the century.

A +3OC world is unlivable.

Even worse, business as usual puts us on a path toward 4OC (7.2OF) or more by 2100. +4OC is beyond unlivable.

Seven: Where do we set our goals?

Even the goal of 1.5OC (2.7O F) set in the Paris Agreement is incompatible with life as it has evolved on planet Earth over the last several million years.

Where, then, do we set our goals?

We need to achieve climate stability by 2100 below 1.0oC (1.8OF) above pre-industrial averages.

In terms of level of accumulated CO2 emissions of, we need to stabilize by 2100 at or below 350 ppm, still far above the pre-industrial maximum of 280 ppm.

Eight: Current emissions vs accumulated emissions

We know from the paleoclimate record that global temperatures rise and fall in step with the level of accumulated emissions, as measured by the atmospheric concentration of CO2 (now around 412 ppm). The increase in the Earth’s temperature that we are now experiencing is due to accumulated past emissions that have resulted in CO2 levels of 412 ppm.

The emissions that we are dumping into the atmosphere today -- our current emissions -- only make the existing problem worse.

The first step in solving the climate crisis is stopping to make the problem worse. We do so by getting our current emissions net zero as soon as possible. And we start to fix the problem itself by removing accumulated atmospheric carbon by means of one or more “negative emissions” or “atmospheric carbon dioxide removal, or CDR” strategies.

But let’s remember: it’s not an either/or. Net zero as soon as possible and removal of atmospheric CO2 are complementary and compulsory!

Nine: Negative emissions, or atmospheric carbon removal

The amount of atmospheric carbon dioxide removal needed to restore climate stability is not known with any degree of precision. It depends on big variables like: the rate of future emissions, the response of the Earth’s climate system, including unknown climate feedbacks and tipping points.

Our options for negative emissions or atmospheric carbon dioxide removal fall into two broad categories:

1. Nature-based solutions (usually known as sequestration). These solutions, including planting and managing forests, regenerative agriculture (carbon farming), managed grazing, and wetland and ocean restoration, have been working well for millions of years. Nature has been reliably cycling carbon since long before we arrived on the scene.

In addition, nature-based solutions provide a long list of co-benefits: creation of habitat, increased biodiversity, increased agricultural productivity, increased soil water retention, increased air quality, and more. Nature-based solutions represent our best near-term option

2. Technology-based solutions include bioenergy with carbon capture and storage (BECCS), biochar, direct air capture and carbon sequestration (DACCS) and enhanced mineralization.

Unlike nature-based solutions, technology-based carbon dioxide removal solutions are largely theoretical, unproven at scale, expensive, and offer few co-benefits.

In the words of New Yorker writer Elizabeth Kolbert, technology-based carbon removal “...has become vital without necessarily being viable. It may be impossible to manage and may also be impossible to manage without.”

We’ll leave it there for now.

Ten: Facing up to climate reality

We’ll admit it: facing up to the reality of the climate crisis is hard. It inevitably brings some measure of despair, of anger, of hopelessness. We would all prefer to change the channel, to not have to think about an unlivable Earth.

We are sometimes counselled to avoid talking about the grim consequences of our climate pollution. We are told, correctly, that fear is not a good motivator and leads more directly to disengagement than to action.

But we must speak the truth.

As catastrophic wildfires, floods, heat waves, and droughts become annual events in Sonoma County, we are already being confronted by the grim consequences of the climate crisis. Changing the channel is not an option.

Opportunity is the flip side of adversity. Now is our time to examine and re-imagine how we live our lives, how we organize our towns and cities, how we move ourselves and our stuff from place to place, how we build our houses, how we grow our food and dispose of our wastes.

Our job is to re-think “how we’ve always done things.”

Now is our time to shine!

Now is our chance to Imagine Sonoma County!