The Pathways To Different Climate Change Temperature Scenarios (1.5, 2, 3, 4 & 4+ Degrees Celcius)

The Pathways To Different Climate Change Temperature Scenarios (1.5, 2, 3, 4 & 4+ Degrees Celcius)

You might hear about the different warming temperature scenarios for climate change.

1.5 Degrees celcius and 2 degrees get all the attention because these are often the ones identified by the IPCC and at the Paris Agreement for example.

But warming may go beyond these temperatures to 3, 4 and 4+ degrees in the future (if we don’t introduce meet the current emission targets, or introduce new emission goals and policies).

In this guide, we look at exactly what it would take to get to each of these temperatures – the pathway of quantity of emissions in what amount of time.

 

Summary – Where Are We Realistically Headed In Terms Of Global Warming In The Future?

There are several variables that impact our emissions, and level of warming in the future.

Climate models can give us a forecast based on the variables and data fed into them, but, those variables and the data can change as we do more or less to impact our emissions, and we get updated data on how the climate is responding.

From a range of studies and reports, the most likely warming range is anywhere between 2.6 to 4.8 degrees celcius above pre-industrial levels. But aggressive action by countries like China and the US immediately in terms of reducing emissions and sequestering existing atmospheric emissions could reduce that estimate.

We should note that 0.8 to 1.2 degrees of warming has already taken place since the start of industrial times.

You can read more about the forecasts and projections for climate change and global warming in the future in this guide.

 

1.5 Degrees, & 2 Degrees Are The Preferred Warming Targets, But…

  • The carbon budget is the amount of carbon dioxide emissions we can emit while still having a likely chance of limiting global temperature rise to 2 degrees celcius above pre-industrial levels.
  • This budget is roughly around 1 trillion tonnes of C02.
  • As of 2011, we’ve already gone through 52% of the budget
  • The world can stick within the budget if countries commit and stick to international C02 emissions pledges, countries pursue and introduce their own C02 reduction measures, emissions peak by 2020 and in 2040 emissions are 50% of 2020 levels and after steadily decreasing, and roughly three quarters of remaining fossil fuels stay in the ground.

BUT…

  • If emissions continue at their current rate, the world is on track to exceed the carbon budget (for 2 degrees) by around the year 2045
  • The general consensus is that it’s extremely unlikely we can still limit warming to 1.5 degrees
  • The general consensus is that we can still limit warming to 2 degrees, although it’s going to require very ambitious and immediate action from all countries to reduce emissions. 

– wri.org

 

What Are The Different Pathways Of Emissions That Lead To Different Warming Temperatures

Note – the following are just a few of many forecasts by different climate modes trying to calculate emission pathways and associated warming in the future.

They are more of a calculated guess with the information we have available right now, rather than an absolute certainty.

Carbon budgets and emission pathways have been adjusted in the past.

 

There are 4 emissions pathways we might see in the future:

  • Low Emissions, Global Temp Increases By Up To 2 Degrees Celcius – In this scenario, C02 emissions peak by 2020, and then drop 66% below 2010 levels by 2050.
  • Medium Emissions, & Global Temp Increases By Up To 2.9 Degrees Celcius – In this scenario, C02 emissions peak by 2040, but still rise 19% above 2010 levels by 2050. By the year 2056, the carbon budget is exhausted, locking in a 2 degrees increase.
  • High Emissions, & Global Temp Increases By Up To 3.7 Degrees Celcius – In this scenario, C02 emissions peak by 2080, but still rise 34% above 2010 levels by 2050. By the year 2057, the carbon budget is exhausted, locking in a 2 degrees increase.
  • Highest Emissions, & Global Temperature Increases By Up To 4.8 Degrees Celcius  – In this scenario, annual C02 emissions continue to rise through 2100, rising 108% above 2010 levels by 2050. By the year 2045, the carbon budget is exhausted, locking in a 2 degrees increase.

– You can read more, including the impacts on earth, humans, animals and the environment at each of these scenarios and pathways at https://www.wri.org/ipcc-infographics

 

On 6 October 2018, the IPCC Summary For Policymakers Special Report was produced.

This report outlines the following for 1.5 degrees celcius warming:

  • The amount of C02 that can be produced in every year into the future, and the amount of black carbon, methane and nitrous oxide
  • The characteristics of four illustrative model pathways to limit warming to 1.5 degrees celcius

You can check it out at http://report.ipcc.ch/sr15/pdf/sr15_spm_final.pdf

 

Sources

1. https://www.wri.org/ipcc-infographics

2. http://report.ipcc.ch/sr15/pdf/sr15_spm_final.pdf

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