More than five years after Pres­i­dent Oba­ma and oth­er lead­ers agreed on a 2020 goal of rais­ing $100 bil­lion each year from pub­lic and pri­vate sources to help devel­op­ing coun­tries deal with cli­mate change, the Unit­ed Nations wants to see action.

Ahead of Earth Day on Wednes­day, U.N. Sec­re­tary-Gen­er­al Ban Ki-moon is point­ing to a meet­ing next month in New York where he says he will be look­ing for clear indi­ca­tions from gov­ern­ments and investors as to how the ambi­tious goal will be reached.

“Cli­mate change is the defin­ing issue of our times,” he told a con­fer­ence host­ed by Bloomberg New Ener­gy Finance last week. “It is also an enor­mous eco­nom­ic opportunity.”

On Sat­ur­day Ban again tack­led the sub­ject, at an Inter­na­tion­al Mon­e­tary Fund event in Washington.

“We need a cred­i­ble tra­jec­to­ry for real­iz­ing the $100 bil­lion goal per year by 2020, as well as the oper­a­tional­iza­tion of the Green Cli­mate Fund,” he said.

“This was a com­mit­ment which was made in 2009 dur­ing the Copen­hagen cli­mate change sum­mit meet­ing. We have only mobi­lized $10 bil­lion as an ini­tial cap­i­tal­iza­tion of this Green Cli­mate Fund. I would real­ly hope that there will be a tra­jec­to­ry, a path, which will be shown to the member-states.”

And at a pre-Earth Day con­cert on the Nation­al Mall in Wash­ing­ton, D.C., on Sat­ur­day night, Ban called on con­cert-goers to raise their voic­es in support.

“I want to hear from you,” he told the crowd. “It’s our last chance to slow glob­al warming.”

Launched in 2011 as a result of that 2009 deci­sion in Den­mark, the Green Cli­mate Fund (GCF) is designed to help devel­op­ing coun­tries curb “green­house gas” emis­sions and cope with occur­rences blamed on cli­mate change, such as ris­ing sea levels.

The aim is to reach $100 bil­lion a year by 2020.

As of April 10, the fund had received pledges from 33 coun­tries, total­ing $10.2 bil­lion. That includes a $3 bil­lion pledge by Oba­ma last Novem­ber, by far the largest con­tri­bu­tion promised to date. Some GOP law­mak­ers have sig­naled an inten­tion to push back.

The next big date on the inter­na­tion­al cli­mate cal­en­dar is a U.N. cli­mate mega-con­fer­ence in Paris in Novem­ber that is meant to deliv­er a new glob­al agreement.

Ban and U.N. cli­mate offi­cials want clar­i­ty on the financ­ing issue, as a con­fi­dence boost­er ahead of the Paris gathering.

Sub­si­dies in the fir­ing line

Accord­ing to the World Bank, two key ways for gov­ern­ments to free up fund­ing to help achieve the $100 bil­lion tar­get is by “putting a price on car­bon” – through car­bon tax­es or emis­sion trad­ing schemes – and phas­ing out fos­sil fuel subsidies.

“With a small per­cent­age of the mon­ey that saved by end­ing sub­si­dies or of the rev­enue raised from a car­bon tax or per­mit sale going to cli­mate finance, gov­ern­ments could help meet the $100 bil­lion cli­mate finance com­mit­ment and oth­er mit­i­ga­tion and adap­ta­tion needs,” it said in a report Sat­ur­day on the IMF and World Bank spring meet­ings in Washington.

A coali­tion of eight coun­tries – Cos­ta Rica, Den­mark, Ethiopia, Fin­land, New Zealand, Nor­way, Swe­den and Switzer­land – is tar­get­ing the sub­sidy issue in par­tic­u­lar. The coali­tion, call­ing itself “Friends of Fos­sil Fuel Sub­sidy Reform,” said on Fri­day gov­ern­ments spent more than $548 bil­lion on fos­sil fuel sub­si­dies in 2013.

The group not­ed point­ed­ly that this was more than five times more than the $100 bil­lion tar­get for cli­mate mit­i­ga­tion and adap­ta­tion by 2020.

“The elim­i­na­tion of fos­sil fuel sub­si­dies would make a sig­nif­i­cant con­tri­bu­tion to the goal of keep­ing aver­age tem­per­a­tures from ris­ing more than two degrees Cel­sius above pre-indus­tri­al lev­els,” the coali­tion added, refer­ring to the goal which world lead­ers sev­er­al years ago decid­ed was nec­es­sary to avoid what glob­al warm­ing advo­cates say will be poten­tial­ly cat­a­stroph­ic effects on the planet.