More than 2,000 academics from over 80 countries – including linguist Noam Chomsky, climate scientist Michael E Mann, philosopher Peter Singer, and historian Naomi Oreskes – have called on world leaders to do more to limit global warming to a 1.5C rise.

In an open letter, they write that leaders meeting in Paris at a crunch UN climate summit next week should “be mustering planet-wide mobilisation, at all societal levels” and call for citizens around the world to hold their leaders to account on the issue.

The world has already warmed by 1C above pre-industrial levels. Holding warming to 1.5C would be a far greater challenge than the 2C that leaders at previous climate talks have agreed to limit rises to. Current emissions pledges tabled ahead of the Paris summit would see warming of around 2.7-3C.

They say that such a rise is: “profoundly shocking, given that any sacrifice involved in making those reductions is far overshadowed by the catastrophes we are likely to face if we do not.”

Separately, the CEOs from 78 companies collectively worth over $2tn – among them Nestlé, Accenture, HSBC, Lloyd’s, Microsoft, BT Group, PepsiCo, Siemens, SOHO China, UniLever, PwC, Marks & Spencer and the Mahindra Group – have pledged their support to governments to implement ambitious targets.

The companies, which operate in more than 150 countries, call for support for alternative energy sources, a carbon price to bolster investment, “consistent policies and robust monitoring” and for greater disclosure on investments related to fossil fuels and alternative energies.

In a letter co-ordinated by the World Economic Forum, the corporations recognise the internationally agreed target to limit global warming to 2C.

They write: “climate change is one of the biggest global challenges that will shape the way we do business now and in the coming decades. This coalition ... believes the private sector has a responsibility to actively engage in global efforts to reduce greenhouse gas (GHG) emissions, and to help lead the global transition to a low-carbon, climate-resilient economy.”

It also extends an “open offer” to governments to “co-design tangible actions”, reduce their emissions and energy consumption and incorporate climate risk into their business strategies.