Everything You Need To Know About Climate Science In Seven Words
Zero emissions. Pretty darn soon. Methane first.
I’m a systematic learner. When I approach a new subject, I like to start with the foundations and work my way up.
When it comes to the science of climate change, this has totally not worked for me. The topic is overwhelming.
If you, like me, have been feeling overwhelmed by the complexity of climate science, then I have some good news. In a little bit I’ll talk about how I reached my breaking point. (That’s not the good news.) But I’ll also explain why you can feel fully qualified to discuss the topic and take action without diving deep into the science.
Plenty of important subjects are too complex for a layperson to fully absorb. But sometimes, a short phrase can encapsulate everything you actually need to know. For example, consider nutrition. You might have seen this beautiful distillation:
Eat food. Not too much. Mostly plants.
These seven words1 contain a lot of wisdom about processed foods, snacking, portion control, and food choice. Sure, you might benefit from studying nutrient charts, tracking your fiber intake, and computing the glycemic index of your meals. But you’ll do pretty well just by following those seven words. And as fascinating and confusing as climate science can be, most of what you and I need to know can also be summarized in seven words:
Zero emissions. Pretty darn soon. Methane first.
Before I explain this, let me walk you through the process that got me there.
You Thought The Main Greenhouse Gas Was CO₂ But It’s Actually Water Vapor
This is the straw that broke my personal camel’s back.
You’re probably familiar with the basic concept of the “greenhouse effect”. To review, an actual greenhouse is a building with glass walls and roof. Glass is transparent to visible light, but not to infrared (heat) radiation. Energy flows in as sunlight, is converted to heat, and can’t get back out; hence, greenhouses are warm. As everyone always points out, this is also why cars get so boiling hot when left in the sun.
The Earth functions a bit like a greenhouse, because a number of gases in the atmosphere behave like glass – transparent to visible light, but not infrared. We all know the largest contributor is carbon dioxide (CO₂). So imagine my surprise when I learned, only recently, that this isn’t true! From an IPCC report2:
Water vapour is the primary greenhouse gas in the Earth’s atmosphere. The contribution of water vapour to the natural greenhouse effect relative to that of carbon dioxide (CO₂) depends on the accounting method, but can be considered to be approximately two to three times greater. … One may therefore question why there is so much focus on CO₂, and not on water vapour, as a forcing to climate change. [emphasis added]
One may question why, indeed! I’ve spent a year reading about climate change, and I never encountered the fact that CO₂ isn’t even the main player?!?
These Questions Have Answers, But There Are Too Many Questions
As it turns out, climate change is in fact driven by CO₂3. It’s just that the process is more complicated than I’d understood. The majority of the direct greenhouse effect comes from water vapor, but the amount of water vapor in the atmosphere is determined by CO₂ (and methane, etc.). Briefly:
We emit CO₂.
This warms the atmosphere.
Which then absorbs more water vapor (through evaporation).
Which warms the atmosphere even more.
CO₂ isn’t the strongest component of this process, but it’s the controlling factor. It’s the steering wheel; water vapor is the engine.
This is an interesting bit of climate trivia, but it also highlights the difficulty of trying to do first-principles calculations. For instance, suppose you wanted to estimate the net warming impact of an additional gigaton of CO₂. Water vapor is just one of dozens (hundreds?) of important effects you’d need to take into account. From carbon cycles to thermal inertia (atmospheric, land, shallow ocean, and deep ocean), albedo effects, seasonal cycles… it goes on and on.
It’s just too much to absorb.
It’s Fine, We Constantly Make Good Decisions About Things We Don’t Really Understand
Suppose I wake up with sniffles, a cough, or sore throat. (For simplicity, assume it’s not Covid.) I don’t really know how to tell a cold from the flu, or precisely what the latest medical statistics say about the potential medical implications of either. But I pretty much know what to do: take it easy, avoid other people, call my doctor if it gets worse. These basic rules of thumb, grounded in professional advice plus common sense, may not be precise – I don’t know exactly what constitute the medically optimal symptom thresholds for calling my doctor or heading to urgent care – but precision isn’t really necessary. Slightly sick, no worries. More sick, get advice. Suddenly very sick, seek immediate care.
We routinely make important decisions about systems we don’t fully understand. How much to save for retirement. Whether to wear sunscreen today. What time to leave for the airport. These all have two things in common: there are reasonable rules of thumb, and it’s not necessary to get the answer exactly right.
Here’s Basically Everything You Need To Know About The Science Of Climate Change
Even scientists need sophisticated computer models to put all the pieces together and cough out an estimate of how the climate will behave under a given scenario. Fortunately, thousands of people all over the world have come together, under the umbrella of the IPCC, to summarize the situation for us. And by now, I’ve spent enough time reading IPCC reports, and various people’s analyses of those reports, to realize that it all boils down to this:
To rein in climate change, we need to net-zero our emissions of CO₂, methane, and a few other gases.
To avoid unnecessary short-term problems, we should address methane and a few other short-lived greenhouse gases early.
All of this is doable.
The problem is serious enough to merit urgency, but not so dire as to merit desperation. Every month we waste increases global suffering, but we’re already doing well enough to avoid the really bad global doomsday scenarios4.
In other words: Zero emissions. Pretty darn soon. Methane first.
Wait So The Scientific Answer is “Pretty Darn Soon”?
Exactly how urgent is it to reach net zero? Is it absolutely imperative to limit warming to 1.5°C? If not, what limit is acceptable? And given a target, precisely how fast do emissions need to come down to hit that target?
There’s no precise answer to these questions. On a scientific level, the models give a range of possible outcomes. On a societal level, there’s no objective way to balance the impact of warming against the effort needed to bring down emissions faster.
Fortunately, we don’t need precision. I don’t know exactly how highly we should prioritize emissions reduction, but it’s clear that few (if any) states or countries are prioritizing it enough. So we should keep pushing for more. At the same time, the situation does not look truly catastrophic, so desperate fanaticism is not called for. (Not to mention that desperation is a poor way to rally people to your cause.) For you and me as individuals, any level of effort in that fuzzy middle ground between “business as usual” and “despair” constitutes a pretty reasonable course of action.
This is why I say that we need to zero out our emissions “pretty darn soon”. The idea is to convey a level of importance and urgency that is significant, but not overwhelming. Honestly, I think that’s as much as the science can tell us, and as much as we really need to know.
Anyone Talking About “The One Big Thing Everyone Missed” Is Confused
I frequently see people making dramatic proclamations about the climate, claiming to have noticed a fundamental fact that is not being discussed. “Just based on historical emissions, we’ve already locked in 2.5°C of warming.” “When we stop burning coal, the lack of sulfur aerosols will cook the planet.” “All of the forests are going to burn.” Or alternatively, “we just need to plant more trees and everything will be fine, why is everyone making such a fuss?”
These statements generally have three things in common:
They point out some important factor that the mainstream discussion has supposedly overlooked.
There is a dramatic implication, usually negative (it’s too late, we’re all doomed), sometimes positive (there’s no climate problem, we just need to do X, usually “planting trees”).
The argument is fatally flawed. Sometimes the math is simply wrong, but often it’s a failure to take the the entire climate system into account. For instance, it’s true that we’re due for extra warming when we halt sulfur emissions, but other factors can counterbalance that. When someone says “the mainstream scenarios omit X”, the truth is generally “no, they know about X; you forgot that it’s counterbalanced by Y”.
The IPCC work is really, really thorough. The odds are low that someone will come along and notice a basic scientific fact that was somehow not taken into account.
Worry About What To Do, Not Whether To Do Anything
I’ve claimed that the implications of climate science are simple:
Zero emissions. Pretty darn soon. Methane first.
The complicated part is how we get to zero emissions. This job – “mitigation” – entails transforming every part of the world economy. This is a hugely complex undertaking. But the complexity is not about climate5; it’s about technology, engineering, industry, economics, policy, and consumer choice.
Fortunately, these don’t interrelate quite as ferociously as the various aspects of climate science do. You can make an immense contribution if you’re just working on alternative materials or wind power… or just voting for candidates who support climate progress, or buying an EV.
This is where it gets interesting. As I discussed in Mind the Gaps, there are a zillion things that need doing. Some are more effective than others; some are more neglected than others. But to make a difference, there’s no need to understand the entire system. Just worry about the bit you’re trying to change.
IPCC AR5 WG1, chapter 8, 8th page of this PDF. (Or weirdly, according to the page numbering used in the report: page 666.)
Actually, of course, not just CO₂; the other things we’ve been told are “greenhouse gases”, such as methane, also contribute.
Of course the impact will be uneven, and some areas or communities will be severely impacted. But global devastation no longer seems to be in the cards.
For effective adaptation – becoming more resilient to the effects of the changing climate – we do need to look into the details of what climate science tells us is in store, region by region. But that’s a separate project from mitigation.
Can you write a little more about “methane first” and what that means in terms of your actions and funding, if applicable?