Carbon Efficiency

Last updated on 2025-02-14 | Edit this page

Overview

Questions

What is the difference between global warming and climate change?
What is the difference between climate and weather?
What are greenhouse gases (GHGs)?
What does the term carbon equivalence (CO₂e) mean?
How is climate change monitored and reported?

Objectives

Understand key terms in environmental sustainability.
Understand what CO₂e means.
Understand how changes in the climate are monitored.

Introduction

Understanding the impact of greenhouse gases on our environment is key to understanding HPC’s own carbon footprint. You will learn about the different kinds of greenhouse gases present in the environment, how they are emitted and measured, and what is being done by different organisations around the world to control and reduce these emissions.

You will find out about the GHG protocol and what it means for green use of HPC.

Key concepts

Global warming vs climate change

Global warming is the long-term heating of Earth’s climate system observed since the pre-industrial period (between 1850 and 1900) due to human activities, primarily fossil fuel burning. Climate change is long-term shifts in temperatures and weather patterns. These shifts may be natural, but since the 1800s, human activities have been the main driver of climate change.

Climate vs weather

Weather refers to the conditions of the atmosphere in a short period of time. Climate refers to the conditions of the atmosphere over long periods of time. Any changes to the long-term condition of the atmosphere will also cause changes to the short-term conditions. Some examples of measurable changes to weather conditions due to climate change are:

Changes to the water cycle, including rainfall
Melting of ice
Heating of the land, air, and ocean
Changes in ocean currents, acidity, and salinity

These changes can lead to flooding - both in coastal areas and due to increased rainfall - drought, wildfires and more frequent extreme weather conditions.

Greenhouse gases and the greenhouse effect

Greenhouse gases are a group of gases that trap heat from solar radiation in the Earth’s atmosphere. These gases act as a blanket, increasing the temperature on the surface of the Earth. This is a natural phenomenon which has been accelerated due to man-made carbon emissions. Now the global climate is changing at a faster rate than that at which animals and plants can adapt.

Greenhouse gases and the greenhouse effect are crucial to all life on Earth and often come from natural sources like animals, volcanoes, and other geological activity. The greenhouse effect allows the Earth to maintain a higher temperature than it would without them by capturing more heat from solar radiation. Like many other natural processes of the Earth, the greenhouse effect is a balance that can be upset by multiple factors.

Carbon and CO₂e

Carbon is often used as a broad term to refer to the impact of all types of emissions and activities on global warming. CO₂e (sometimes: CO₂eq/CO₂-eq), which stands for carbon equivalence, is a measurement term used to measure this impact. For example, 1 ton of methane has the same warming effect as about 84 tons of CO₂ over 20 years, so we normalise it to 84 tons CO₂e. We may shorten even further to just carbon, which is a term often used to refer to all GHGs.

Monitoring climate change

As a result of the effects of climate change and an ever-increasing number of destructive weather events, efforts have been made by the global community to address these issues and take steps to control and limit global warming in order to mitigate and reverse the effects of climate change.

The Paris Climate Agreement is an international treaty agreed in 2015 by 196 parties and the UN to reduce the Earth’s temperature increase. The agreement is to keep the rise in global mean temperature to 2°C compared to pre-industrial levels, with a preferable lower limit of 1.5°C. The agreement is reviewed every five years and mobilizes finance to developing nations to mitigate the impacts of climate change and prepare for and adapt to the environmental effects caused by climate change. In addition, each party is expected to update its progress through a Nationally Determined Contribution (NDC). As of October 2024, 195 parties, including the UK, have joined the agreement.

The United Nations Framework Convention on Climate Change (UNFCCC) is a group created to achieve the stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous interference with the climate system.

The COP (Conference of the Parties) is an annual event involving all parties in the United Nations Framework Convention on Climate Change. At the conference, each party member’s progress on tackling global warming, as agreed as part of the Paris Climate Agreement, is reviewed and assessed. The COP is also a chance for parties to come together and make decisions that will reduce the effects of global warming. Common topics include strategies to reduce carbon, financing low carbon strategies and preservation of natural habitats.

The IPCC (Intergovernmental Panel on Climate Change), created by the UN in 1988, aims to provide governments at all levels with scientific information that they can use to develop climate policies. IPCC reports are also a key input into international climate change negotiations. The IPCC is an organization of governments that are members of the United Nations or the World Meteorological Organization (WMO). The IPCC currently has 195 members.

We will always emit carbon through our activities, but being carbon efficient means minimising the amount of carbon emitted per unit of work. We aim to ensure that for each gram of carbon we emit into the atmosphere, we extract the most value possible.

Picture of user minimising carbon emissions

In the HPC space, the part we play in the climate solution is using HPC in a carbon efficient way. Being carbon efficient is about making sure your use of HPC emits the least carbon possible for the work we are doing. Or, for providers of HPC systems, it means procuring and operating the system in such a way as to minimise the carbon emissions. Ideally, you would also be able to quantify the positive carbon impacts from the work (or HPC system itself) to understand the overall net impact on carbon emissions - though doing this is typically quite challenging.

Positive emissions impacts

As well as reducing emissions from our use of HPC there are typically other sources of positive carbon emissions impact associated with HPC

The main source of reduced emissions from HPC use is in the research that leads to new technology, policies and approaches to reducing emissions. Some examples include:

HPC services run the climate models that are used to provide evidence for setting emissions reductions policies and targets across the world. Research and modelling on HPC services leads to development of improved zero emission energy generation by, for example, modelling new wind turbine and wind farm designs.
Modelling to support the development of new energy storage technologies such as improved batteries.

The emissions reductions from such activities are extremely difficult to quantify for a number of reasons so, at the moment, these are not factored in to the emissions estimates for HPC systems and research more broadly but you should be aware of them and think about how they might apply to your research in particular.

As well as the research activities on HPC systems leading to reductions in emissions, there are other activities that HPC services can potentially take to have positive emissions impacts, for example:

Using the waste heat generated by large scale HPC services as a heat source for homes, businesses or farming. For example, the LUMI HPC system in Finland is connected to the district heat network for the local city of Kaajani and helps heat homes and businesses.
Incorporating environmental and biodiversity improvements into the service. For example, for the ACF data centre that hosts ARCHER2 (which is in a rural location) EPCC have been working to improve the site biodiversity and improve habitats.
Responsible carbon offset schemes could also potentially be used to reduce emissions if they are undertaken as part of providing an HPC service.

Exercise: Positive emissions impacts

Write down the outcomes or activities that you do as part of your research or work that could be produce positive carbon emissions. Once you have them written down, can you rank them in order of what you think the largest source of emissions will be to the smallest? Can you think of any way in which you might go about quantifying this positive impact so it could be included in a carbon audit of your work?

Show me the solution

You may have come up with outcomes such as:

Key Points

Greenhouse gases are a group of gases contributing to global warming. Carbon is often used as a broad term to refer to the impact of all types of emissions and activities on global warming. CO₂e is a measurement term used to measure this impact.
The international community, in groups such as the UNFCCC, has come together to limit the impact of global warming by reducing emissions, aiming for a ‘preferable’ lower limit of 1.5°C. This was agreed through the UN IPCC in 2015 in the Paris Climate Agreement and is monitored at the regular COP event.
Everything we do emits carbon into the atmosphere, and our goal is to emit the least amount of carbon possible. This constitutes the first principle of green software use: carbon efficiency, emitting the least amount of carbon possible per unit of work.