We're currently trapping 1.16 watt/m² of energy.
This causes temperatures to rise by 0.3 °C per decade
and makes unusual weather events happen 3.5 times more often.
Earth's energy imbalance is the difference between the amount of energy arriving from the sun on the planet's surface and the amount of energy radiated back into space. Greenhouse gas emissions produced by human activities are increasing Earth's energy imbalance. They make it harder for the energy to escape, trapping it in the Earth system instead.
The energy coming from the sun drives all weather patterns on the planet: rain and snow, cold and heat, wind and storms. The more solar energy we trap, the more we alter and supercharge the weather. That's why Earth's energy imbalance can be thought of as the main driver of climate change.
Since 2010, Earth's energy imbalance has more than doubled, from 0.5 watt/m² in 2010 to 1.05 watt/m² by the end of 2022. This means that we are trapping additional energy at an ever faster rate.
Imagine you're standing on the beach wearing a jumper and trousers. The sun is shining, and it's not too hot or too cold — you feel perfect. At that moment, there is a balance between the energy (light) arriving from the sun and the energy (heat) radiated by your body into the surroundings.
Now someone throws a dark blanket over you. This additional layer absorbs the light from the sun and makes it harder for your body heat to escape. As more energy gets trapped by the blanket, you start to feel hotter and hotter. You experience a heating imbalance.
If you throw off the blanket and take off your jumper, your body heat can escape easier, and you start cooling down again. You are now experiencing a cooling imbalance.
Earth's energy imbalance changes naturally with the seasons. It also fluctuates from year to year, mostly because of changes in ocean currents. If the Earth's energy flows were balanced, the average value of Earth's energy imbalance over longer periods of time (for example, the 10-year average) would be close to 0 watt/m².
The 10-year average of Earth's energy imbalance is now consistently positive, meaning there is more energy trapped in the Earth system. This happens because greenhouse gas emissions from human activities act as a blanket. They make it harder for the heat to escape, trapping it instead.
Earth's energy imbalance is measured in watt per square metre.
Watt is a unit to measure power. This is the use or flow of energy:
The unit of Earth's energy imbalance is expressed in watt/m² - or watt for every square metre on Earth. The number of square metres across the whole of the Earth's suface is enormous. When you sum up all the energy being trapped across all of those square metres, the total amount is unimaginably large.
There are roughly 510,000,000,000,000 square metres of surface on Earth. By comparison, there are almost 8.1 billion people. Written in full, it looks like this: 8,200,000,000. This means that there are about 64,000 square metres for every person on the planet. At the current rate, it means we are adding roughly 72,000 watts of energy for every person. That means that, on average, we are trapping as much heat in the Earth system as if every person on the planet is continuously running 36 ovens, side-by-side, with their doors open.
The energy arriving from the sun drives all weather on the planet.
The more of that energy we are trapping, the more we are altering and supercharging the weather. It can create stronger rainfall; lead to longer droughts and hotter heatwaves; strengthen winds and storms; or disturb the global ocean currents.
The value for Earth's energy imbalance is a 10-year average calculated from CERES satellite data, which is maintained by NASA and the US National Oceanic and Atmospheric Association (NOAA).
Climate change is usually reported in terms of the total level of temperature change relative to a pre-industrial period - usually the period from 1850 to 1900. According to this metric, global average temperatures have gone up by +1.27°C since pre-industrial times.
This number for the total level of temperature change obscures that most of the warming (+0.9°C) has happened in the last four decades alone. To show how fast the climate is changing right now, we need another metric in addition to 'level': the speed of temperature change.
The relationship between the level and speed of temperature change is similar to that between distance and speed when travelling in a car or on a bike:
Both distance and speed are needed to work out when we can expect to reach our destination.
Different parts of the world are warming at different speeds. In regions like Europe and East Asia (consisting of countries like China, Japan and Indonesia) temperatures are going up faster than the global average. Other regions (like Australia and the US) are warming more slowly than the global average.
There are many reasons for these regional differences. In general, land mass is warming faster than the oceans, and regions further north or further south from the Equator are warming faster than regions closer to the Equator. Another reason is changes in the dominant ocean and wind currents around the planet. These are changing because of the additional energy trapped in the Earth system (see the Imbalance metric above).
The graph also shows the total level of temperature change for each region (in the 'total' box). Level and speed together give the complete picture of how much total warming each region has already experienced, and how fast it is changing right now.
The speed of temperature change is expressed in degrees celsius per decade. A speed value of +0.3°C/decade means that the level of temperature went up by +0.3°C over the last decade.
Global and regional temperatures vary naturally from year to year and over longer timescales. In a world without climate change, the speed of temperature change would still fluctuate but it would average out at 0°C/decade. Since the 1980s, however, the speed of temperature change has been increasing, averaging around +0.2°C/decade.
The total level of warming has been used worldwide to measure climate change as well as to set targets to keep a liveable planet. The UN Paris agreement, for example, states that we should try to keep warming to well below 2°C and pursue efforts to limit it to 1.5°C above pre-industrial levels.
If temperatures keep rising at the current speed, then we will hit 1.5°C by 2031-2032. The 1.5°C threshold, however, is not an absolute limit between 'safe' and 'unsafe'. With the current level of warming of 1.27°C, many regions around the world are already experiencing the devastating effects of heatwaves, droughts and floods. Going over 1.5°C, on the other hand, does not automatically mean that it is 'game over' for society or too late to do anything about climate change.
As we approach 1.5°C of global warming, the debate about the importance of this limit is becoming more fractious. Some people argue that we should 'keep 1.5°C alive' at all costs, whereas others say it's too late. The speed metric offers a way out of this stand-off. It has a natural threshold of 0°C/decade, not a politically-agreed one like 1.5°C or 2°C. Instead of focusing on when we'll reach the arbitrary thresholds of 1.5°C or 2°C, this metric offers the opportunity to say:
"Every additional +0.1°C of warming will make climate change much more disruptive to my area, my country, and the world."
Another way of explaining that temperatures are going up by +0.3°C/decade is to say that roughly every 3.3 years Earth is warming +0.1°C. So at our current speed of warming, every 3.3 years we are making it vastly more difficult to tackle the consequences and disruptions of climate change.
The value for the speed of temperature change is a 10-year average calculated from global and regional temperature datasets maintained by Berkeley Earth.
The speed of temperature change shows how fast the average temperatures are changing, but the daily temperature extremes are changing rapidly too. Whether it's an extremely hot day during summer, or an unusually warm day during the colder months, climate change is causing temperature records to be broken more often than before.
The unusual weather index combines information from weather stations all over the world to work out how often high-temperature records are being broken, and compares that to the number of record-breaking temperatures we would expect to see if there was no climate change. The resulting number is a measure of how unusual the weather is becoming.
The index captures the extremely hot days for each location, for example, the +40°C heatwave which happened across much of Europe in summer of 2022. It also captures record-breaking temperatures that are not extreme in an absolute sense. For example, New Year's Day 2023 reached 16.2°C in the UK - the hottest New Year's Day on record. It was very unusual, though not 'extreme' in the sense of unpleasantly or dangerously hot.
All regions are experiencing more record-breaking temperature events, but to different degrees. In 2021 (the year this data is for), Europe witnessed far more unusual temperatures than the global average. Russia and Australia experienced fewer than the global average - but still more than would be expected in a world without climate change. East Asia (consisting of countries like China, Japan and Indonesia) and the US witnessed about the same number of record-breaking temperature events as the global average.
For now, the unusual weather index looks at the number of times high temperature records are broken. It can be calculated for other aspects of weather too, such as rainfall quantities.
Values for the last 30 years of the unusual weather index show that the number of record-breaking temperature events is going up. The index varies year-on-year due to natural variability in the Earth's climate system, but the overall trend for the last three decades is increasing.
In a world without climate change, the unusual weather index would vary around a value of 1.
The unusual weather index is now consistenly above 1; clearly showing the effects of climate change on the occurence of record-breaking temperatures.
The unusual weather index is calculated from weather station data maintained by the US National Oceanic and Atmospheric Association (NOAA). Analysis of the data and construction of the metric was performed by Dr Selma Guerreiro (Newcastle University) and Chris Parker (WSP).
Find out more on the UCL Climate Action Unit Climate Change in Numbers project page
Metric design by: