theSIGNAL SCIENCE
8 November 2026
"The first principle of science is that you must not fool yourself, and you are the easiest person to fool."
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Science

Humans Now Exhale 2 Billion Tonnes of CO2

A new study finds that human metabolism now releases 2.05 billion metric tons of carbon dioxide a year, but not all carbon is equal.

You are doing it right now. Every few seconds, you push carbon dioxide out of your lungs, and so do roughly eight billion other people. Has anyone ever added it all up? A team led by the University of Bath has done exactly that.

Their estimate, published in The Lancet Planetary Health, is that human metabolism released 2.05 billion metric tons of CO2 in 2015. Thirty years earlier, in 1985, the figure was 1.18 billion.

That is a rise of 74%. Surprisingly, the average person did not become much more productive at exhaling. More than 60% of the increase was attributed to a simpler cause: there are more of us. In the words of Professor Javier Gonzalez, who led the work, the rise is mainly because there are more people on the planet.

Before anyone feels guilty about breathing, a distinction matters. The carbon in your breath mostly comes from your food, and that food grew from plants that pulled CO2 out of the air only recently.

Photo: RODRIGO GONZALEZ / Unsplash
Commuters crowd a busy city street, each person quietly exhaling carbon dioxide with every breath.
Discuss
  • Why does the origin of carbon matter more than the amount when comparing breath with fossil fuel emissions?
  • The study found population growth drove most of the rise. What does this suggest about how we frame climate responsibility?
  • How might measuring human metabolic CO2 more precisely improve the accuracy of climate predictions and policy decisions?
Science

Europe's Ancient Forests Were Mostly a Myth

Picture Europe a million years ago. Did you imagine endless, shadowy forest? Aarhus University researchers say that image is probably wrong. Their study suggests meadows, scattered trees and grassy clearings dominated for over 20 million years, kept open by giant grazers. Dense forest may be the newcomer.…
  • If Europe's natural landscape was open, should reforestation programs stop prioritizing dense forests?
∞
We all produce carbon dioxide simply by turning food into energy, but until now we haven't had a good idea how much that adds up to worldwide.
Professor Javier Gonzalez, Centre for Exercise, Nutrition and Metabolism, University of Bath
Science

The Moon That Refused to Go Cold

China's Chang'e-5 probe brought home a puzzle in 2020: volcanic rock only 2 billion years old. The Moon should have been dead by then. Cooling after its birth, roughly 4.5 billion years ago, was meant to be fast. So what kept it warm? Radioactive decay and asteroid strikes were both ruled out as too weak or too early. A new study from Chengdu suggests gravity itself did the kneading.…
  • If Earth's gravity kept the Moon volcanic, what might it mean for other moons?
GLOBAL · Science
An anti-aging drug may help protect the brain before Alzheimer's symptoms begin
EUROPE · Science
Future warming events will outdo the extreme heat waves of the recent past, new study finds
AMERICAS · Science
Permanent daylight saving time has a dark side, scientists warn
OCEANIA · Science
First direct observations reveal hydrogen dissolved in tiny gaps between metal atoms
theSIGNAL IN THE LAB
1VOCABULARY
metabolismattributed to
ledgerlocked undergrounddominated
ruled outpuzzle
2GRAMMAR FOCUS
Discourse markers — contrast and concession (Nevertheless, Whereas, Despite)
Use 'Whereas' or 'While' to contrast two facts in one sentence, 'Despite' or 'In spite of' before a noun or -ing form, and 'Nevertheless' or 'However' to begin a new sentence that contrasts with the previous one. 'Although' introduces a full clause of concession.
Whereas · Despite · Nevertheless · Although · However · In spite of · While
  1. Human breath released 2.05 billion tonnes of CO2 in 2015, the figure in 1985 was only 1.18 billion.
  2. the rise in total emissions, the average person did not become much more productive at exhaling.
  3. Breathing out CO2 may sound alarming. , the carbon in our breath comes mostly from recently grown plants.
  4. coal and oil release carbon that was locked underground for millions of years, a farmer's wheat returns carbon to a loop that was already turning.
  5. the fact that breath emissions are small, counting them makes the global carbon books more reliable.
  6. Researchers say meadows and clearings dominated Europe for over 20 million years. , Danish subsidies still reward only dense planting.
3DEPENDENT PREPOSITIONS
Complete each phrase with the correct preposition. All from today’s articles.
  1. The rise was attributed ___ a simple cause: there are more of us.
  2. A distinction matters before anyone feels guilty ___ breathing.
  3. Dense forest may be the newcomer, kept at bay ___ giant grazers for millions of years.
  4. Scientists need to judge whether emission-cutting policies are succeeding ___ hoped.
  5. Radioactive decay and asteroid strikes were both ruled ___ as too weak or too early.
4CRITICAL THINKING
All three stories overturn something we assumed was settled: how much carbon people release, what Europe once looked like, and how the Moon stayed warm. Why do you think such basic assumptions survive for so long before anyone tests them? Choose one story and explain what kind of evidence or new technology made the old assumption impossible to defend.
5CREATIVE · HEADLINES
Write a headline for the top story in each of the following styles. One line each, no explanation:
  • TABLOID NEWSPAPER
  • LUXURY MAGAZINE
  • ACTIVIST BLOG
6WRITING
Write a short paragraph (80-100 words) about a 'hidden' or overlooked factor in your own life, something that quietly shapes your days but rarely gets noticed, as the Earth's pull did for the Moon. Explain how you first became aware of it.
7DEGREES OF EXTREMITY
Complete each ladder from mild to strong.
  • surprising→→
  • large→→
  • old→→
  • wrong→→
  • warm→→
  • uncommon→→
8SPEAKING
  1. Which would unsettle you more: a surprising scientific discovery or a startling one?
  2. Is it better to learn that a famous belief is mistaken, or completely false?
  3. Why do you think scientists find ancient history so compelling?
  4. Can a scientific measurement ever be absolutely vital without being widely noticed?