Climate, end to end

01

Earth's breathing

Since 1958, scientists have measured the CO₂ in the air on the Mauna Loa volcano in Hawaii, far from cities and factories. It may be the world's most important graph: from 315.7 ppm (parts per million) in 1958 to an average of 427.3 ppm in 2025. Before industrialisation it was around 280 ppm.

The curve breathes

Zoom in and you see a sawtooth. That is the plants. Most of the planet's land, and so most plants, is in the Northern Hemisphere. As they grow in spring and summer they pull CO₂ out of the air and the curve falls. In autumn and winter leaves and plant matter decay and the CO₂ comes back. The peak usually comes in May, the low in September–October. In 2025 the swing was 6.1 ppm.

But notice: every new peak is higher than the last. The plants breathe; we keep adding. In 2024 the annual mean rose 3.52 ppm, the largest rise in the whole record, and in 2025 2.74 ppm · own calculation from NOAA's monthly data.

02

Where does it come from, and where does it go?

In 2025 humanity emitted about 42.2 billion tonnes of CO₂: 38.1 from coal, oil and gas (a new record) and 4.1 from deforestation and other land-use change. That is about 5 tonnes for every person on Earth own calculation. So where does it go?

Over the past decade plants and soil on land took about a fifth, the ocean about 29%. The rest, roughly half, stays in the atmosphere, and that is what makes the curve above climb. Nature's help has also got weaker: climate change has made the land and ocean sinks together almost 20% smaller than they would otherwise be.

03

The trees and you

There are about 3 trillion trees on Earth. Before humans began clearing forest there were about 5.6 trillion. Each year about 15 billion are cut down and 5 billion planted.

Plants are most of life: about 80% of all carbon in living things is in plants, above all in tree trunks and roots. Humans themselves are almost nothing by comparison. Shared out among all of us, the plants' carbon equals about 200 tonnes of CO₂ per person.

And one last comparison: around 2020, everything humans have built and made (concrete, asphalt, metal, plastic) came to weigh as much as all life on Earth. Around 1900 it was three percent. In Denmark the goal is to plant a billion trees and grow 250,000 hectares of new forest by 2045.

04

The heat

More CO₂ in the air holds in more heat. 2024 was the warmest year on record: 1.55 °C above pre-industrial, the first full calendar year above 1.5 °C. The World Meteorological Organization puts the chance that at least one year in 2026–2030 will be warmer still at 86%.

05

El Niño, right now

El Niño is a natural swing: every few years the tropical Pacific turns unusually warm and weather shifts across much of the globe. It connects directly to the curve in chapter 1:

1. 1Warm Pacific
2. 2Drought and heat in the tropics, especially the Amazon
3. 3Plants absorb less CO₂
4. 4CO₂ in the air rises faster

During the 2023/24 El Niño the land sink fell by about 2.2 billion tonnes of carbon a year. Almost all of it was in the tropics, half in the Amazon alone. Hence the record rise in 2024. The same pattern was seen in the big El Niños of 1997/98 and 2015/16. Several climate scientists expect the current El Niño to make 2027 the warmest year ever recorded.

06

Your day in CO₂

Big numbers are hard to feel. So here is one that fits a day: an average Dane accounts for about 30 kg CO₂e a day (own calculation: 11 t ÷ 365). Below it is used as the yardstick: how much of a Danish day does one kilo of a food equal?

And on the move, per 100 km per person

Averages for UK conditions (DESNZ via Our World in Data); rail varies a lot with each country's electricity. See Climate facts for detail.

See which stores make it easiest →

07

What to remember

1. CO₂ is still rising, and faster. 2024 had the largest rise ever measured.
2. Nature takes half, but less than before. Land and ocean absorb roughly half our emissions, and climate change is weakening them.
3. Trees cannot clean up after us. All vegetation on land takes back only about 1 of each person's 5 tonnes.
4. What you eat matters more than where it comes from. Except when it is flown. Meat from ruminants is by far the heaviest item in the basket.
5. Train beats plane. Taking the train instead of a domestic flight cuts about 86% of the trip's emissions.
6. El Niño brings swings; the direction is ours. This winter's record El Niño changes the speed, not the cause.
7. Habits beat good intentions. Small choices repeated every week move more than one big decision that never happens.