The UK Government representative at the conference and the outgoing Cop26 president criticised elements of the deal, in his speech at the closing plenary session of the UN climate summit.
While he said that progress on loss and damage has been “historic”, he warned that it was not a moment for “unqualified celebration”.
Officials and negotiators agreed a deal in the early hours of Sunday that will create a fund for compensating poor nations that are victims of extreme weather worsened by rich countries’ carbon pollution.
It is a big win for poorer nations which have long called for cash because they are often the victims of climate worsened floods, droughts, heat waves, famines and storms despite having contributed little to the pollution that heats up the globe.
But Mr Sharma indicated that the deal did not go far enough, as he told the closing session: “Many of us came here to safeguard the outcomes that we secured in Glasgow, and to go further still.
“In our attempts to do that, we have had a series of very challenging conversations over the past few days.
“Indeed those of us who came to Egypt to keep 1.5 degrees alive, and to respect what every single one of us agreed to in Glasgow, have had to fight relentlessly to hold the line.
“We have had to battle to build on one of the key achievements of Glasgow.”
Mr Sharma’s speech, delivered after what appeared to be fraught and last-minute efforts to broker a consensus, pointed out the gaps in the agreement.
“We joined with many Parties to propose a number of measures that would have contributed to this. Emissions peaking before 2025, as the science tells us is necessary.
“Not in this text.
“Clear follow-through on the phase down of coal. Not in this text.
A clear commitment to phase out all fossil fuels. Not in this text.
“And the energy text, weakened, in the final minutes.”
He continued: “Friends, I said in Glasgow that the pulse of 1.5 degrees was weak.
“Unfortunately, it remains on life support.
“And all of us need to look ourselves in the mirror, and consider if we have fully risen to that challenge over the past two weeks.”
First Minister Nicola Sturgeon hailed the agreement to establish a fund for loss and damage as “truly groundbreaking” but hit out at the lack of progress elsewhere.
“I am pleased that Scotland, in being the first developed country ever to make a financial contribution, has been able to play a small part in that journey working with others over the last twelve months to build the momentum that has led to today’s decision.
“There remains a lot of detail to be worked out over the next year ahead of COP28, but from the inclusion of loss and damage on the agenda, to the agreement to establish a fund, this COP has delivered a real breakthrough for vulnerable and developing countries.
“It is deeply disappointing that the recognition of loss and damage has not been matched by greater action to prevent a worsening of the climate crisis. Keeping 1.5 alive and delivering the fastest possible transition away from fossil fuels is key to preventing greater loss and damage in the future. Alongside loss and damage we needed to see progress on adaptation and mitigation, on the submission of new national contributions, a pathway to 2030 and a strengthening of the language of the Glasgow Pact.”
The slogan of “keeping 1.5 alive” dominated discussions at the summit in Glasgow last year, as Mr Sharma and the UK steered efforts to limit global warming.
The target comes from the Paris Agreement, the global treaty on climate change negotiated in 2015, where there was a strong and ultimately successful push by nations such as low-lying islands to include the 1.5C target in the deal because they felt letting temperatures go any higher would threaten their survival.
Governments and experts will now closely consider what the deal means in the fight against climate change.
On Sunday morning, many campaigners praised the breakthrough on the loss and damage fund, which according to the agreement will initially draw on contributions from developed countries and other private and public sources such as international financial institutions.
But it came alongside warnings that time was running out to curb global warming.
Friends of the Earth’s international climate campaigner Rachel Kennerley said: “Wealthy countries must now support the setting up of this fund – and crucially its financing – to ensure it reaches the frontline communities hardest hit by the climate crisis.
“Countries like the UK must now provide the necessary cash, and ensure the scheme isn’t undermined by nations trying to avoid their obligations,” she said.
But she accused rich countries of also using the talks to “avoid ending their addiction to coal, oil and gas – instead favouring dangerous and ineffective distractions, like offsetting, over cutting emissions”.
Yeb Sano, who headed up the Greenpeace delegation at Cop, said that the agreement of the fund marks a “new dawn for climate justice”, adding that it proves “if we have a long enough lever, we can move the world”.
Katie White, executive director of advocacy and campaigns at WWF, said: “While a deal on loss and damage finance is a positive step, it risks becoming a down payment on disaster unless emissions are urgently cut in line with the 1.5C goal.”