Temperatures could continue to rise long after net zero carbon goals are met

Global temperatures may continue to rise for centuries even if climate goals to cut human-induced greenhouse gases to net zero are successful, a study has found.

A simulation of the global climate between 1850 and 2500, which has been published in Scientific Reports, has modelled the global temperature and sea level rises during that time period.

The modelling suggests that under conditions where greenhouse gas emissions peak during the 2030s and decline to zero by 2100, global temperatures will be 3 degrees Celsius warmer and sea levels 3 metres higher by 2500 than they were in 1850.

Under conditions where all manmade greenhouse-gas emissions are reduced to zero during the year 2020, the authors estimate that, after an initial decline, global temperatures will still be around 3°C warmer and sea levels will rise by around 2.5 metres by 2500, compared to 1850.

Even without additional carbon being pumped into the atmosphere, continued melting of Arctic ice and carbon-containing permafrost may increase emissions of the greenhouse gases water vapour, methane and carbon dioxide.

Melting of Arctic ice and permafrost would also reduce the area of ice reflecting heat and light from the sun.

To prevent the projected temperature and sea level rises, the authors believe that all manmade greenhouse gas emissions would have had to be reduced to zero between 1960 and 1970.

To prevent global temperature and sea level rises after greenhouse gas emissions have ceased, and to limit the potentially catastrophic impacts of this on Earth’s ecosystems and human society, at least 33 gigatonnes of carbon dioxide would need to be removed from the atmosphere each year from 2020 onwards through carbon capture and storage methods.

Such a suggestion has already been made by the International Energy Agency, which said in September that carbon capture technology is essential for climate goals to be met.

Today, the UK’s largest retailer Tesco announced plans to set up solar farms, fit more solar panels in its stores and roll out electric vehicles, in order to make it a net zero carbon business by 2035.

It has set up a new partnership with renewable energy investor Low Carbon that will see three solar farms set up in Anglesey, Wales, and in Essex and Oxfordshire in southern England.

The farms will generate up to 130GWh of energy per year and Tesco will procure more renewable energy from the national grid including five onshore windfarms.

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