The Paris Agreement was struck in 2015 with the hope that nations would come together to prevent climate change from becoming an existential crisis for billions of people worldwide.

As countries take the next steps on the Paris pact this fall and a global movement gathers steam to urge world leaders to do more to avert the worst consequences of global warming, they will be doing so in a world that looks different today than it did three years ago.

Just in the past 12 months, new indicators of how global warming is changing the planet have mounted:

The record for the largest wildfire in California’s history was broken—twice. The hottest nighttime low temperature ever seen on Earth—108.7 degrees Fahrenheit (42.6 Celsius), recorded in Oman. Record heat waves baked the Arctic Circle and Japan. Some property values are falling because of rising sea levels along the East Coast.

Though none of these extremes necessarily indicates that global warming trends have suddenly become more acute, they still affect how people feel about what climate change means for them.

“Climatewise, you would be very hard pressed to argue that you can detect a difference between 2015 and 2018,” Gavin Schmidt, director of the NASA Goddard Institute for Space Studies, told Bloomberg Environment. “You could make a stronger case that perceptions have changed as a function of exactly when we got the warmest years, and specific floods, heat waves, fires etc.”

Those perceptions of a changed world and recent climate milestones will likely play heavily into talks at the Global Climate Action Summit in San Francisco Sept. 12-14.

Companies and local governments at the summit plan to declare how they’re cutting their carbon footprints and pushing national leaders to exceed their commitments to the Paris pact. New information about climate change and its impact on people also is expected to influence international climate negotiations at the United Nations Framework Convention on Climate Change in Katowice, Poland, Dec. 3-14, where the details on implementing the Paris Agreement will be finalized.

Here are five ways the world has changed since the Paris climate agreement was struck in 2015.

*1 - 400 Parts Per Million of Carbon Dioxide: No Going Back

Carbon dioxide accumulates in the atmosphere as humans burn more fossil fuels, and the more of it there is, the warmer the Earth becomes.

NASA confirmed in 2017 that concentrations of carbon dioxide in the atmosphere reached a milestone: 400 parts per million as measured at the Mauna Loa Observatory in Hawaii.

It was globe’s highest level of carbon dioxide in the atmosphere in at least 400,000 years.

Although largely symbolic, 400 ppm shows that human-generated carbon dioxide emissions are accumulating in the atmosphere faster than the Earth’s ability to absorb them, warming the planet.

Carbon dioxide concentrations before the Industrial Revolution in the late 1700s were around 280 ppm and had increased to 380 ppm by 2005. As of July, concentrations were 408 ppm, according to NASA data.

“The carbon dioxide in the atmosphere continues to climb at ever-faster rates and there is no sign of even a flattening, let alone a turn down,” Kevin Trenberth, a climate scientist at the National Center for Atmospheric Research, told Bloomberg Environment. “So far, Paris has not made a visible dent. The Earth is in trouble.”

*2 - 2015 was Earths hottest year on record. And then 2016 was.

The Paris climate accord was struck during 2015—the world’s hottest year on record at the time. Then 2016 became the hottest year on record, followed by 2017 coming in third.

So far, 2018 is on track to rank among the top five. That continues an inexorable warming trend that has led to 17 of the Earth’s 18 warmest years on record to have occurred since 2001, according to NASA.

The goal of the Paris Agreement is to try to halt global warming at 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial levels, and not let it exceed 2 degrees Celsius (3.6 degrees Fahrenheit) of warming.

In 2016, average global temperatures reached nearly 1 degree Celsius (1.8 degrees Fahrenheit) of warming since 1880.

*3 - The Oldest Arctic Sea Ice has Begun to Melt

For the first time, satellite imagery captured this year showed that the Arctic’s oldest, thickest, and stablest sea ice has begun to melt and break free from the coast of Greenland because of warmer surface air temperatures linked to climate change.

It suggests that global sea-level rise will accelerate because the main driver of rising seas—the melting of the Greenland ice sheet—also will accelerate, and the Earth could soon see its Arctic polar ice cap vanish entirely in summertime, possibly in less than 10 years, Peter Wadhams, a University of Cambridge ocean physics professor whose research has chronicled the loss of Arctic sea ice for decades, told Bloomberg Environment.

“The loss of ice in summer is very radical,” he said. “It’s not just sea ice retreat that is really harming the planet. It’s the fact that loss of sea ice causes other things which are worse.”

The melting of the polar ice cap means more of the sun’s energy is absorbed by the Arctic Ocean. That causes the jet stream to slow down, leading to more extreme heat or extreme cold for longer periods of time in the U.S. and Europe. And it melts Arctic permafrost, which releases methane into the atmosphere and accelerates global warming, Wadhams said.

*4 - Better Tools Link Climate Change and Extreme Weather

Since 2015, scientists have become better equipped at detecting the effects of global warming and the fingerprints of climate change on devastating extreme weather such as Hurricane Harvey, Katharine Hayhoe, a climate scientist at Texas Tech University, told Bloomberg Environment.

Attribution science, the field that links heavy rains, severe floods, intense hurricanes, wildfires, and other extreme weather events to climate change, has advanced significantly in three years, according to Hayhoe.

New satellite data since 2015 show that seas are rising faster then previously thought, and scientists have been able to more clearly document how high-tide flooding due to rising seas is affecting coastal cities, she said.

“New satellite sensors and techniques have allowed scientists to more accurately estimate changes in sea-ice thickness,” Jennifer Francis, a marine sciences professor at Rutgers University, told Bloomberg Environment. “New measurements have provided more accurate estimates of ice-sheet melt.”

*5 - Climate-Change-Fueled Disasters Played Live on TV

Millions across the globe watched in 2017 as Puerto Rico was devastated by Hurricane Maria and Houston flooded during Hurricane Harvey, which is tied with Hurricane Katrina as the costliest hurricane in U.S. history.

“The impacts of climate change have played out in real time, on our television screens, in the form of unprecedented floods, droughts, wildfires, and heat waves,” Michael Mann, a climate scientist at Penn State University, told Bloomberg Environment. “The impacts of climate change—in the U.S., and around the world—are no longer subtle.”

That, together with new scientific data about climate change and images of record-breaking California wildfires and other extreme global weather events, could now be affecting how some scientists, policy makers, and the public think about climate change.

“The public sees with their own eyes—and feels with their own wallets—the effects of bizarre weather, rising sea levels, changing animal habits, destructive fires, and toxic algae blooms. Increasingly they are asking why and listening to experts who can provide fact-based answers rather than the disinformation generated by those who stand to lose as our economy shifts away from fossil fuels,” Francis said.

But seeing still may not be believing, at least in the U.S., Rachael Shwom, a Rutgers University sociologist studying how people make sense of climate change, told Bloomberg Environment.

“Gender and political ideology Democrat/Republican are the most consistent predictors of concern about climate change,” Shwom said.

“While we would expect increasing number of weather events and ability to provide scientific attribution to increase awareness and concern about climate change most research has shown that political ideology overwhelmingly influences the interpretation of these weather events,” she said.