Irreversible changes, warmer temperatures sooner: 5 alarming findings from the UN climate change report
A grim global report on climate change released Monday paints a dire picture for the future of Earth.
Climate change has led to irreversible shifts for the next hundreds to thousands of years, according to the report from the United Nations' Intergovernmental Panel on Climate Change (IPCC). The effects of more extreme weather are felt across the globe, the report said, and average global temperature increases that could have devastating effects may come sooner than expected.
Dubbed a "code red for humanity" by the United Nations, the report says unequivocally humans have caused climate change, driven up greenhouse gas emissions and led to warmer weather.
'Code red for humanity': UN report gives stark warning on climate change, says wild weather events will worsen
Here are five of the most alarming findings in the climate report:
We may reach 1.5°C of warming much sooner than previously expected
"One of the most striking takeaways is that we may reach 1.5°C of warming a decade earlier than the IPCC had previously found," said Helen Mountford of the World Resources Institute.
Warming of 1.5 degrees Centigrade would increase heat waves, lengthen warm seasons and shorten cold seasons. If temperatures were 2 degrees warmer, heat extremes would more often reach critical tolerance thresholds for agriculture and health, the report says.
In five scenarios of expected levels of greenhouse gas emissions laid out in the report, global warming of at least 1.5 degrees is the best estimate for the increase in temperature in the near term, from 2021 to 2040. Even under the lowest emissions scenarios, the report says a 1.5-degree warming in the next 20 years is "more likely than not" before bouncing back. Previous predictions did not expect this level of warming this soon.
The five scenarios varied more in how much global temperatures will increase in the coming century, but even under a very low greenhouse gas emissions scenario, the range of temperature increase by 2100 is very likely to be 1 to 1.8 degrees Centigrade.
Human-caused climate change is already affecting 'every region across the globe'
No region of the globe has been spared from the impacts of climate change, the report says. Climate change is "affecting many weather and climate extremes," such as heat, heavy precipitation and drought.
Since the IPCC's last assessment, the evidence of humans' influence on specific weather events has strengthened.
The report says extreme heat has become more frequent and more intense across most parts of the world since 1950. The IPCC asserts with "high confidence" that human-caused climate change is the main driver and that without human influence, some of the extreme highs would be "extremely unlikely."
Heavy precipitation has increased in frequency and intensity across most regions, the report said.
The report found the share of hurricanes that reach the devastating levels of Category 3 to 5 storms has probably increased over the past 40 years. Humans have increased the chances of extreme compound weather events, such as the frequency of concurrent droughts, fire weather and flooding.
Extreme weather will get worse
The report found a direct relation between increasing temperatures and extreme weather events. For every half a degree Centigrade warmer the average global temperature is, expect "clearly discernible increases" in extreme heat waves, heavy precipitation and droughts.
For example, hot temperature extremes that typically occurred only once every 10 years without human-caused climate change are likely to occur 4.1 times if temperatures increase by 1.5 degrees Centigrade. If temperatures increase by 2 degrees, a once-in-every-10-years extreme is likely to occur 5.6 times. Under a 4-degree warming scenario, the extreme heat occurs 9.4 times.
Each incremental increase in global temperature would lead to lower levels of Arctic sea ice, snow cover and permafrost.
Under all five emission scenarios the report lays out, the Arctic is likely to see at least one September month that is practically free of sea ice before 2050.
Many changes to Earth are irreversible for centuries and millennia
In a number of areas, greenhouse gas emissions have caused irreversible damage, and the effects will be felt on the time scale of centuries to millennia, according to the report.
The report says ocean temperature changes and ocean acidification, mountain and polar glacier melt and sea level rise are all expected to continue over the next hundreds of years regardless of human intervention.
Over the next 2,000 years, even if global temperatures are kept to a 1.5-degree increase, the average global sea level is expected to rise 2 to 3 meters.
The report says ice loss in Greenland over the 21st century is virtually certain and there is high confidence that ice loss will increase cumulative emissions.
As emissions and temperatures increase, Earth's water cycle becomes more intense
Earth's natural cycles are expected to be acutely effected by rising global temperatures and greenhouse gas emissions, the report says.
As the climate warms, Earth's water cycle will increasingly tend to more extremes. In some areas, that means wetter wet seasons and in others drier dry seasons, the report says.
Increased variability in rainfall tied to El Niño is very likely under three of the global emission scenarios.
The way Earth naturally combats increased carbon emissions is likely to be affected in the coming decades, the report says.
Earth's carbon sinks – generally its forests and oceans – will store an increasing amount of carbon under scenarios with higher emissions, but they will be less effective in the higher emission scenarios, the report says. As a result, higher levels of emissions will remain in the atmosphere.
Contributing: Doyle Rice