The latest report from the United Nations' Intergovernmental Panel on Climate Change (IPCC) is out and it paints a bleak picture. The report notes: "It is unequivocal that human influence has warmed the atmosphere, ocean, and land."

The report also does a new evaluation of the "carbon budget"—the amount of carbon dioxide and equivalent emissions that can be added to the atmosphere to stay under a given temperature. IPCC's definition for carbon budget:

"The term carbon budget refers to the maximum amount of cumulative net global anthropogenic CO2 emissions that would result in limiting global warming to a given level with a given probability, taking into account the effect of other anthropogenic climate forcers. This is referred to as the total carbon budget when expressed starting from the pre-industrial period, and as the remaining carbon budget when expressed from a recent specified date. Historical cumulative CO2 emissions determine to a large degree warming to date, while future emissions cause future additional warming. The remaining carbon budget indicates how much CO2 could still be emitted while keeping warming below a specific temperature level."
IPCC

Like our favorite confusing term, embodied carbon, the carbon budget is not well understood and not well-named. It should probably be called a carbon ceiling because it, as the graph notes, is cumulative. Every metric ton of CO2 emissions adds to global warming. Every kilogram. Every ounce.

Our World in Data

We will be hitting the carbon ceiling soon: In 2019 the world pumped out 36.44 billion metric tons or metric gigatons of CO2. It took a drop in 2020 thanks to the pandemic but is likely back up for 2021.

Carbon ceilings - IPCC

We will say it again: It's cumulative. As the IPCC notes in this chart, since 1850 we have pumped 2,390 metric gigatons of CO2 into the atmosphere and raised the temperature about 1.92 degrees Fahrenheit (1.07 degrees Celsius). To have an 83% chance of keeping the temperature rise under 2.7 degrees Fahrenheit (1.5 degrees Celsius) we have a ceiling of 300 metric gigatons. At the 2019 rate of emissions, we blow through the ceiling in 8.2 years; we don't even get to that 2030 deadline when we are supposed to have cut our emissions in half.

World Steel Association

This is why I keep stressing the importance of embodied carbon are so important. These are the emissions that come from making things, be it buildings, cars, or computers, as opposed to the operating emissions from burning things like gasoline for transportation or natural gas for heating.

These upfront emissions are generally ignored, but they are significant; just making the steel that goes into our cars, buildings, and washing machines total 8% of annual emissions. According to the World Steel Association, the industry produced 1,875,155 thousand metric tons of steel in 2019. That alone is responsible for 3.46 metric gigatons of CO2 emissions at 1.85 metric tons per metric ton of steel, in one year. It's mostly in that big blob over China, but much of it comes back to us in solid form. As Kai Whiting and Luis Gabriel Carmona wrote in "The hidden cost of everyday products":

"Heavy industry and the constant demand for consumer goods are key contributors to climate change. In fact, 30% of global greenhouse gas emissions are produced through the process of converting metal ores and fossil fuels into the cars, washing machines and electronic devices that help prop up the economy and make life a little more comfortable."
World Green Building Council

I keep coming back to this graph demonstrating how to reduce the carbon emissions from buildings because it applies to everything, from cities to cars to computers.

We have to stop building stuff we don't need. We have to build smaller and make less stuff. We have to build clever and "lightweight" everything, using the least amount of material to do the job, whether it is moving people or housing them. We have to make everything last longer. We have to electrify everything and we have to stop burning fossil fuels.

We know how to do all of this, and we know where the carbon ceiling is. We know that every ounce of CO2 emissions adds to global warming and that it's cumulative, which is why we have to do this now.