"We believe in the significance of this event as we face global challenges to secure energy, water and food and to address the consequences of climate change," Sheikh Mohammed told the notable audience at the Abu Dhabi National Exhibition Centre.
"We in the UAE have always supported and called for concerted efforts by the international community, governments, companies and creative individuals, all with the aim of developing the desired solutions.
"We need to exert all possible efforts because the future depends on the steps we take today."
Throughout the week, government leaders, clean-energy investors, scientists and advocates will convene in Abu Dhabi.
The French president, Francois Hollande, also addressed the opening, with a stern warning.
"If we do not act ... you can be very sure we will have a catastrophe very soon," he said.
Mr Hollande said governments needed to unite in cutting greenhouse emissions and avoid climate change.
He reiterated France's offer to host the 21st Conference of the Parties of the United Nations Framework Convention on Climate Change in Paris in 2015 – the deadline set for world governments to sign a new global treaty on reducing emissions to replace the Kyoto Protocol.
Scientists say failure to act by then could mean catastrophic climate change is unavoidable.
The Argentine president, Cristina Fernandez de Kirchner, said rich countries needed to accept their responsibility and do more to reduce their emissions.
"Rich countries have a pattern of energy consumption that is not sustainable," Ms de Kirchner said.
Industrialised countries emit on average three times more greenhouse gases per capita than emerging economies, she said.
The gap is even larger if their per capita emissions are compared to those of poorer developing nations. "We are all responsible," said Ms de Kirchner.
"But of course, some of us have more responsibility than others."
Yesterday's ceremony also opened the World Future Energy Summit, the International Renewable Energy Conference, and the first International Water Summit.
Dr Sultan Al Jaber, the chief executive of Abu Dhabi's clean-energy company Masdar, said the focus on sustainable managing water resources was of crucial importance to the Emirates.
"In the UAE, a nation with the fifth-largest proven oil reserves, our leadership believes that water is more important than oil," Dr Al Jaber said.
Water and energy require the urgent attention of world leaders, who should consider their inter-dependence, he said.
About 7 per cent of the world's energy is consumed to draw, treat and distribute water, while nearly half of the world's water is used in extracting energy resources and producing electricity.
"Here in the [Arabian] Gulf, a region that accounts for 20 per cent of global oil supply and nearly 50 per cent of the world's desalination capacity, the relationship between water and energy is even more crucial," said Dr Al Jaber.
The sustainable management of energy and water resources will require "creating the necessary regulations and policies, forging public and private partnerships and driving the investment required to deliver real solutions".
"Realising actions on such a scale may be viewed by some as a challenge," said Dr Al Jaber.
"However, the UAE views this as a unique opportunity – an opportunity to expand sectors, diversify the economy and establish policies to drive investment."