Taking action to stay within 1.5ºC

Transforming the global energy system

to combat climate change

We need to halve global emissions by 2030

Despite the near unanimous global support to fight climate change, global emissions are still on the rise, and the concentration of greenhouse gases in the atmosphere has never been higher. In 2018, annual global greenhouse gas emissions reached an estimated 54 gigatonnes, the highest level ever recorded.

Without further action, emissions are projected to increase in the coming years, which is in stark contrast to what is required. To keep global warming below 1.5°C, greenhouse gas emissions need to be reduced from 54 to 26 gigatonnes by 2030, and approach net zero by 2050. Reaching ‘net zero’ means that actual emissions do not need to reach zero, as long as any remaining emissions are balanced by removing carbon from the atmosphere. For example, in 2050 it would be possible to absorb emissions of around 7 gigatonnes per year if our planet’s ability to act as a ‘carbon sink’, capturing carbon dioxide, is preserved and enhanced.


Of the 54 gigatonnes of greenhouse gases emitted today, approximately 40 gigatonnes or 73% are related to energy, mainly the combustion of fossil fuels (coal, oil and natural gas). The majority of these emissions can be attributed to electricity and heat production, transportation and energy used for manufacturing and construction.

The largest individual source of emissions is electricity and heat production, accounting for 17 gigatonnes of total emissions, while more than 8 gigatonnes can be attributed to transportation. Emissions from ‘other fuel combustion and fugitive emissions’ include early-stage emissions from coal mining and some non-CO2 emissions from the combustion of fossil fuels.

Annual global greenhouse gas emissions


Sources: Own calculations based on data from: Climate Action Tracker (2019) CAT Emissions Gaps; UNEP (2018) Emissions Gaps Report 2018; Le Quéré, et al. (2018) Global Carbon Budget 2018.

Own calculations based on CAIT/WRI (2014) combined with above data. Note that due to rounding, numbers might not add up to the total amount.

Read more

The need for increased energy efficiency

The less energy we use globally, the easier it will be to decarbonise the energy system in time. However, without substantial improvements in energy efficiency, a combination of increased living standards and global population growth of 2 billion people will cause energy demand to grow a projected 24% by 2050. This is equivalent to adding twice the current energy use of the USA to the world’s current use of energy.

Keeping global energy consumption at the current level would be possible with a global energy intensityCitation Energy intensity is a measure of the energy efficiency of an economy and is measured as the quantity of energy required per unit of GDP.. Improvement of 3.2% per year towards 2050 – up from the current 2.3%Citation IRENA (2019) Global Energy Transformation – Roadmap for 2050.. This can be achieved through accelerated energy efficiency, especially in buildings, alongside electrification. As an example, an electric vehicle is 3 to 4 times more energy efficient than a conventional combustion engine car. Similarly, heat pumps are also more efficient than conventional heating.

Scenarios that limit global warming to an average of 1.5°C necessitate that global energy consumption in 2050 remains at roughly the same level as today, with a green energy share of 60% or moreCitation IPCC (2018) Special Report: Global Warming of 1.5°C; IRENA (2019) Global Energy Transformation – Roadmap for 2050.. If overall energy consumption increases substantially, the total share of green energy must be even higher than 60% in 2050 to limit global warming to 1.5°C. This underlines the importance of increased energy efficiency.

Global supply of energy now and in 2050


Sources: IRENA (2019), Global Energy Transformation – Roadmap for 2050 (2019); IPCC (2018) 1.5 Special Report, Global Warming of 1.5°C.

Green energy must replace fossil fuels in our global energy system 

The global energy system includes all uses of energy for power, transportation, heating, cooling, and industrial processes. Today, around 80% of the world’s consumption of energy is based on fossil fuels (coal, oil, and gas), while the share of green energyCitation Green energy in this paper is defined as energy from renewable resources, excluding traditional biomass.is approaching 11%, up from 8% in 2010Citation REN21 (2019) Renewables 2019 – Global Status Report..

The increasing share of green energy in the global energy system comes from new additions of wind power, solar power, hydro power, and bioenergy, which have added to existing hydro power and bioenergy capacity. However, the overall increase in the share of green energy has been moderate since the use of fossil fuels has also increased in absolute terms, due to a surge in global energy demand caused by population and economic growth.

Current global energy mix

% of total final energy consumption, 2017

11% Green Energy 8% Traditional biomass 2% Nuclear 80% Fossil fuels

Source: REN21: Renewables 2019 – Global Status Report. Numbers are rounded, which explains why they add up to 101%.

Read more

The global share of green energy should reach more than 60% by 2050 to stay within 1.5°C

The current build-out of green energy is simply insufficient to limit global warming to 1.5°C. Without additional action, the share of green energy is projected to reach around 27% of global energy supply by mid-century. In this scenario, average global temperature increase could exceed 1.5°C and approach 2°C by 2050, and put the world on a path to a temperature increase of at least 3°C by the end of the centuryCitation Climate Action Tracker (2019) Warming Projections Global Update..

If we are to limit global warming to 1.5°C however, we must dramatically increase the global share of green energy to at least 60% by 2050Citation The exact share will depend on several factors including: population and economic growth; energy intensity improvements; the role of nuclear; and the extent carbon dioxide removal (CDR) utilisation. Many scenarios are reliant on CDR to some extent, but as CDR solutions are currently based on undeveloped and uncertain technologies, it is unwise to rely heavily on such solutions.. This will require an increase in the share of green energy by almost 1.5 percentage points each year.

Projected vs. required green share in the global energy supply

Sources: IRENA (2019) Global energy transformation: A roadmap to 2050; IPCC (2018) 1.5 Special Report, Global Warming of 1.5°C. Due to challenges in obtaining coherent data, the chart 'Current global energy mix' is based on final energy consumption (11% share of green energy), while this chart and the chart on page 11 are based on total primary energy supply (14% share of green energy). The numbers based on supply are used to be able to compare with IPCC projections.

Transforming the global energy system

If we stay on the current trajectory with existing policies and rates of change, energy demand will continue to increase and fossil fuels will remain dominant in our energy system. In this scenario, we will likely overshoot the critical 1.5°C mark between 2030 and 2052Citation Climate Action Tracker (2019) Warming Projections Global Update.. In the future we should all be striving towards, science suggests that energy efficiency can keep global energy demand at the same levels as today, while green energy rapidly replaces fossil fuels in our global energy system. By taking these steps, we can halve emissions by 2030, and give ourselves the best chance of halting runaway climate change. On the following pages, we explain why we believe that the power sector holds the key to achieving this goal.

Global supply of energy

Exajoules/years and % of green energy

  • Share of green energy
  • Total energy supply, exajoules/year
571 EJ
710 EJ
581 EJ
Sources: IRENA (2019) Global energy transformation: A roadmap to 2050; IPCC (2018) 1.5 Special Report, Global Warming of 1.5°C.

     Continue to

The role of the power sector


Contact us

Interested in getting to know more?

Please do send us an email if you have any questions or enquiries about the content of this paper. Our Global Public Affairs team is here to help.