Paris is the most recent in a series of cities and countries to declare a climate emergency.

“Paris, like other cities, declares a climate emergency,” Celia Blauel, deputy mayor in charge of the environment, told a municipal council meeting, stressing the need to adhere to the objectives of the 2015 agreement.
Before this, New York city, the British Parliament and Ireland’s Parliament declared a climate emergency. Britain’s parliament became the first in the world to declare a climate emergency, passing the largely symbolic motion on May 1, with Ireland’s parliament passing a similar motion on May 10.
The Paris Agreement is an agreement within the United Nations Framework Convention on Climate Change (UNFCCC), dealing with greenhouse-gas-emissions mitigation, adaptation, and finance. Under this, each country must determine, plan, and regularly report on the contribution that it undertakes to mitigate global warming. In 2017 however, Trump announced that the United States would be pulling out of the agreement.
According to The Climate Mobilization, a US NGO pushing for such declarations, some 650 local authorities in cities and towns across the world have now declared a climate emergency.