This year the Earth experienced the warmest April on record, keeping 2016 on track to be the hottest year yet and by the biggest margin ever.

New data released by NASA put this April's land and sea temperatures at 1.11 degrees Celsius warmer than average April temperatures between 1951 to 1980, which NASA uses as a reference point to study recent climate change.

It was the seventh month in a row to rise by at least 1 degree Celsius above the 1951-80 reference averages.

The Reef has suffered two mass bleaching events, in 1998 and 2002, but the extent of the bleaching in these years was less severe than in 2016.

The Reef has suffered two mass bleaching events, in 1998 and 2002, but the extent of the bleaching in these years was less severe than in 2016.

Driven by ocean temperatures that have been 1-2 degrees Celsius (1.8-3.6° F) above average, the bleaching event has left large sections of coral drained of all color and fighting for survival.

Driven by ocean temperatures that have been 1-2 degrees Celsius (1.8-3.6° F) above average, the bleaching event has left large sections of coral drained of all color and fighting for survival.

Of the reefs surveyed in the northern third of the Reef, 81% are characterized as "severely bleached."

Of the reefs surveyed in the northern third of the Reef, 81% are characterized as "severely bleached."

Tourism on the Great Barrier Reef generates an annual income of A$5 billion ($3.9 billion) and employs nearly 70,000 people.

Tourism on the Great Barrier Reef generates an annual income of A$5 billion ($3.9 billion) and employs nearly 70,000 people.

"At some reefs, the final death toll is likely to exceed 90%," Andrew Baird, of the ARC Center of Excellence for Coral Reef Studies, says.

"At some reefs, the final death toll is likely to exceed 90%," Andrew Baird, of the ARC Center of Excellence for Coral Reef Studies, says.

Bleaching occurs when the marine algae that live inside corals die. Of the reefs surveyed in the northern third of the Great Barrier Reef, 81% are characterized as "severely bleached."

Bleaching occurs when the marine algae that live inside corals die. Of the reefs surveyed in the northern third of the Great Barrier Reef, 81% are characterized as "severely bleached."

Some of the bleaching of reefs in the northern section has been described as "extreme."

Some of the bleaching of reefs in the northern section has been described as "extreme."

The different color morphs of Acropora millepora, each exhibiting a bleaching response during mass coral bleaching event.

The different color morphs of Acropora millepora, each exhibiting a bleaching response during mass coral bleaching event.

There are variations in the appearance of severely bleached corals. Here, the coral displays pink fluorescing tissue signalling heat stress.

There are variations in the appearance of severely bleached corals. Here, the coral displays pink fluorescing tissue signalling heat stress.

There are 'winners' and 'losers' among corals as they respond to the accumulating impacts of climate change.

There are 'winners' and 'losers' among corals as they respond to the accumulating impacts of climate change.

The data that just keeps getting worse has prompted scientists to declare a " climate emergency " and is already casting doubts on pledges made in the Paris agreement to keep temperature rises well below the 2 degrees Celsius that scientists say will have catastrophic consequences on the planet.

The agreement was hammered out in December but signed in record-breaking April, with the ambitious aim to cap temperature rises at 1.5 degress Celsius compared with pre-industrial levels.

With Apr update, 2016 still > 99% likely to be a new record (assuming historical ytd/ann patterns valid). pic.twitter.com/GTN9sPL2D7 — Gavin Schmidt (@ClimateOfGavin) May 14, 2016

Leaders also began a 10-day meeting in Bonn, Germany on Monday to follow up on the agreement and to work out just how to make these targets achievable.

Scientists and leaders have agreed that global greenhouse gas emissions will need to peak soon and be followed by quick reductions over the years ahead to contain temperature rises.

"In the second half of the century those emissions need to be so low they can be easily absorbed by the Earth's natural systems such as forests and soils," the U.N. Framework Convention on Climate Change said in a statement.

Temperature rises have had a boost in the past year from a strong El Nino, a weather event characterized by the warming of ocean waters in the tropical Pacific Ocean that brings extreme weather, including drought and heavy rains, to other parts of the world.

There is hope that a La Nina may be creeping in, which typically cools the Pacific waters.

Beyond two degrees

So what happens if the planet breaches the two degrees of warming threshold?

Nothing good, according to reports reviewed by CNN's John Sutter, who has written extensively on the subject.