The world's rapidly growing urban centers should adopt cooling technologies that are cleaner in order to limit greenhouse gas emissions and strengthen the resilience of communities, the U.N. Environment Programme (UNEP) said in a report launched on Wednesday.

According to Beating the Heat: A Sustainable Cooling Handbook for Cities compiled by UNEP and partners, investing in air condition systems that are less carbon-intensive is key to greening the urban environment.

Inger Andersen, executive director of UNEP said that the world metropolises should prioritize cooling systems that consume less energy as they embark on transition to a greener, inclusive and prosperous future.

"Sustainable and equitable urban cooling must be part of cities' efforts to reach net-zero energy targets," Andersen said during the launch of sustainable urban cooling handbook on the sidelines of the 26th U.N. Climate Change Summit underway in Glasgow, Scotland.

The handbook says that warming in cities is likely to hit 4 degrees Celsius given the current rapid emission of greenhouse gases hence undermining the resilience of low-income urban dwellers in the face of climatic shocks.

It warns that diminishing green cover, use of heat-trapping building materials, unsustainable waste management and poor planning has escalated carbon emission in cities.

"With growing populations- predominantly in the tropics- and rapid urbanization, the impact of global warming is felt most acutely in cities. Research shows that the world's cities are heating up at twice the global average," says the handbook.

It says that by 2100, cities across the globe could warm as much as 4.4 degrees Celsius, more than double the Paris Agreement goal of 1.5 degrees Celsius amid carbon-intensive industrial processes, transport and air conditioning.

The handbook adds that hotter cities would have negative impacts on public health, environment, energy systems and economic activities.

While noting that escalating demand for cooling in urban centers that are rapidly warming has put a strain on national power grids, the handbook calls for the adoption of air conditioning practices that emit less carbon into the atmosphere.

"There is an urgent need to transition to more sustainable and equitable ways to cool our cities and ensure access to cooling where needed, without further warming the urban environment," says the handbook.

Andy Deacon, acting managing director, Global Covenant of Mayors noted that cities are at the frontline of the climate crisis hence the need for fiscal and regulatory incentives to boost uptake of greener cooling practices.