Calculating a Climate Future

We all can play a part in reducing carbon emissions. Using the interactive Global Calculator tool, you can determine how your own lifestyle choices and beliefs could impact the eventual world temperature. Environmental writer Mark Lynas walks us through the process, and then invites us to participate.

How does your lifestyle affect the global temperature?

By: Mark Lynas

Talking about climate change is never easy. The debate is fraught with uncertainty, highly politicized, and suffused with a tendency towards moralizing judgments on the part of many participants. In my experience, people shoehorn their visions of the future onto climate change, so anti-capitalists tend to use global warming as a reason to continue to oppose capitalism, while free-marketeers tend to be skeptical about the science because they don't like the idea of government intrusion into markets to regulate carbon emissions.

But, how do our own personal life decisions impact the planet and make for a sustainable or unsustainable future? What if there was a way for one to represent their different preferences with real-world numbers, in order to see what impact they have on the planet?

There is. It's called the Global Calculator, a free, online, open-source, easy to navigate interface where every user can select from a wide variety of different input options on everything from dietary choices to transport patterns, in order to see how their choices stack up in terms of carbon emissions and, ultimately, the resulting eventual global temperature. It quickly becomes evident that there are not only endless ways that we impact our world every day, but also opportunities to help curb our impact.

In order to introduce the tool, which was developed by a team assembled by the late Professor David MacKay (of 'Sustainable Energy: Without the Hot Air' fame), I've plotted out my own numbers below. These are roughly an "ecomodernist" worldview: I want to see a planet where everyone who chooses to can access modern lifestyles, without such an enormous rise in consumption that we end up frying the planet. Is this even possible?

My pathway shows that it is:

The graph shows an early peak in greenhouse gas emissions, and a reduction to below zero by 2100. This results in cumulative emissions below the level necessary to keep the planet's temperature from rising above 2 degrees C, as represented (with shading to show uncertainty) by the thermometer on the right. How did I do it? By making all kinds of different selections from the multiple choices set out below:

The best way to get a sense of how the Global Calculator works is to play with it yourself. My pathway is just one of numerous different alternatives. In general, Level 1 selections allow for increases in consumption and comfort, while Level 4 selections require a tremendous amount of effort. This applies to both the demand and supply sides of the equation.

For example, I've selected from mostly Level 1 on travel, buildings, air conditioning and heating, and so on. This is to reflect the fact that most of the world's population still under-consumes in these areas, so to allow room for growth. I'm allowing a 45% increase in global travel by 2050. I'm also allowing every household in the world to have a refrigerator and other appliances, similar to the average US lifestyle today.

This leads to a lot more energy use. I want this energy to be low-carbon, I have Level 3 solar generation with a massive 4,100 gigawatts of solar capacity by 2050. This is up from around 200 GW today. I have about a tripling of nuclear power capacity worldwide from today (also Level 3) in order to add to the zero-carbon power produced from solar and wind.

Energy — especially electricity — is only a part of the picture, however. Just as important are my selections for global diets, agriculture, and land use. It's worth noting that these issues pertain directly to the mission of the Cornell Alliance for Science. For example, I've selected Level 4 on crop yields:

This means that we need to make a great effort to continue improving yields of major food crops, to reach 100% increase by 2050, either by using genetics or other agronomic approaches (or more likely both). This is important because it can then spare farmland from being ploughed up, and protect the rainforests. Even better, by also constraining the amount of meat people eat globally (meat, especially beef, is a very inefficient way of converting crop biomass into human food energy) I can even spare land for reforestation.

While I allow for everyone to have a healthy caloric intake, global average meat consumption by 2050 would not reach European or American levels, which are too high currently. I'm under no illusions: this would require a huge lifestyle change for many people in rich countries, but it would be healthier for them and the planet. This represents a Level 2 choice, so the global average would be 220 kcal/meat per person per day (the USA average consumption is currently 350 kcal per person).

Speaking of reforestation, this combination of more productive cropland, less meat, and a very low use of bioenergy (so forget biofuels, basically, which are a big waste of land and a threat to ecosystems generally) here's what I can do with forest land (click 'land and food' at the top to get this display):

You will see a dramatic expansion of global natural forest land — basically rewilding — starting from pretty much the current day.

In contrast, what happens if we revert to high meat eating, have extensive grass-fed beef animals, and low-yield agriculture (that is, essentially organic farming planet-wide with high meat consumption)? I get this warning message:

And even if I moderate these choices a little, I still get this:

That's right: unless we make farming much more efficient and restrain the increase in meat consumption, emissions go through the roof. This is an interesting challenge for the agro-ecology movement - the explanatory notes for the calculator's section on crop yields have this to say on the issue of organic farming:

"To represent a move towards an organic farming system in the Global Calculator, crop yields are likely to be lower than industrialised systems, therefore between Level 1 to Level 2 for crop yields would be most appropriate. On a global average, organic crop yields tend to be lower than those of industrialised systems. This would likely result in more land being required to grow crops compared to industrialised systems, and hence could result in deforestation to make way for more agricultural land unless offset to some extent by a concurrent increase in land use efficiency."

Friends of the Earth's pathway of low crop yields and little improvement in farming efficiency does work in the model. . However, in my view, it does so by making heroic assumptions about meat-eating and calorific intake generally: global diets would be heading towards the average in India by 2050 (basically vegetarian). Oh, and there's no nuclear power and lots of renewables, as you might expect.

However, I can't say Friends of the Earth is wrong - their pathway adds up to less than 2C global warming, and that's fine by me. This is the great value of the Global Calculator - it helps us to tease out the assumptions and choices underlying our views of the future and our different ideas about how best to mitigate climate change. There are lots of example pathways: you can scroll through them all using this drop-down menu:

But wait - how do we know these figures are accurate? Maybe the Global Calculator is biased by the sources of the numbers? Well, the tool is entirely open-source - you can even read the minutes of the meetings where the different issues, from buildings to land-use, were discussed, and all the sources for numbers driving the calculator are fully referenced. You can even download the Excel spreadsheet back-end, and update it with your own figures if you like.

Finally, the most important thing is to use the calculator yourself: come up with your own pathway, one which you feel is both realistic and reflects the world you want to live in. Just make sure it keeps the planet's temperature from rising above 2 degrees!

Browse Climate for Change Topics


Share this: