The “carbon clock” is a real-time visualization tool highlighting the urgency of climate change. It provides a dynamic countdown, illustrating the remaining time before global warming is likely to exceed specific limits, such as 1.5°C above pre-industrial levels, if current carbon dioxide emission rates continue. This tool translates complex scientific data into an accessible message, aiming to bring immediacy to climate discussions.
What is the Carbon Clock?
The carbon clock displays the estimated time remaining until a specific global warming threshold is expected to be surpassed. This threshold is often set at 1.5°C above pre-industrial temperatures, a target recognized in international climate agreements. Its purpose is to underscore the need for global climate action by making the abstract concept of climate change more immediate and understandable.
How the Carbon Clock Works
The underlying science of the carbon clock revolves around the concept of a “carbon budget.” This budget represents the maximum amount of carbon dioxide (CO2) that can be emitted globally while still having a reasonable chance of limiting global warming to a specific target, typically 1.5°C or 2°C. For instance, the Intergovernmental Panel on Climate Change (IPCC) estimated in 2021 that, from the beginning of 2020, humans could release an additional 400 gigatonnes (Gt) of CO2 to have a 67% chance of limiting warming to 1.5°C.
The clock calculates the remaining time by dividing this remaining carbon budget by the current global annual CO2 emission rate. For example, the Mercator Research Institute on Global Commons and Climate Change (MCC) carbon clock assumes an average annual emission rate of 42.2 Gt of CO2, or approximately 1,337 tonnes per second. As emissions persist, the remaining carbon budget diminishes, causing the clock to count down faster. While the clock provides a precise measurement, uncertainties exist due to factors like different definitions of the 1.5°C target and assumptions about climate sensitivity.
Implications of the Carbon Clock
The ticking carbon clock serves as a warning system, highlighting the potential consequences if the world exhausts its remaining carbon budget for a specific warming target. When the clock reaches zero for a given temperature goal, it signifies that the carbon budget has been depleted, and the probability of exceeding that temperature threshold significantly increases. Exceeding the 1.5°C limit, for example, is associated with a higher likelihood of more frequent and intense extreme weather events, such as severe heatwaves and extreme precipitation.
Further warming beyond this threshold can lead to impacts like accelerating sea-level rise, increased coastal and river flooding, and widespread ecosystem disruption, including effects on warm-water coral reef ecosystems. These changes can also affect human societies through impacts on health, livelihood, food security, and access to water. The clock highlights that while the world does not end precisely at 1.5°C, surpassing this average temperature makes the repercussions more severe.
Tracking the Carbon Clock
Several prominent organizations and projects maintain and display live carbon clocks. The Mercator Research Institute on Global Commons and Climate Change (MCC) offers its Carbon Clock, which allows users to view the remaining time for both the 1.5°C and 2°C warming targets. Another well-known display is the Climate Clock project, which launched its first monument-sized clock in Union Square, New York City, in September 2020.
These public displays, often found in major cities like London, Prague, Rome, Seoul, and Harrisburg, Pennsylvania, offer a real-time countdown. When accessing these resources online or viewing them in person, individuals will see a digital display showing years, days, hours, minutes, and seconds remaining. These clocks are regularly updated with the latest scientific data, primarily from the Intergovernmental Panel on Climate Change (IPCC), reflecting current emission trends and carbon budget estimates.