How Close Is 1.5°C? Depends When You Measure From

How Close Is 1.5°C? Depends When You Measure From

Most scientists studying global warming compare today’s temperatures to those of the late 19th century because that is as far back as quality temperature observations go. But a new study makes the case for a better comparison period, one that includes the warming that had already resulted by the middle of the 1800s and shows how close the world already is to breaching international warming targets.

Under the landmark 2015 Paris Agreement, countries agreed to cut greenhouse gas emissions to keep global temperature rise “well below” 2°C (3.6°F) above pre-industrial levels and limit it to 1.5°C (2.7°F) above that mark in order to avoid the worst impacts of climate change. But the agreement left undefined exactly what period is considered “pre-industrial.”

How Close Is 1.5°C? Depends When You Measure From Central Credit: Ed Hawkins

Most climate scientists use the second half of the 19th century as a stand-in for pre-industrial times, because of the lack of widespread temperature observations before that point. But as the Industrial Revolution was already underway by then, it is likely that there was already some human-caused warming by that point. A study published in Nature last year found a small, but detectable increase in global temperatures as far back as the 1830s for some parts of the world.

For the new study, detailed Wednesday in the journal Bulletin of the American Meteorological Society.

the authors suggested using 1720-1800 as a pre-industrial period, because it is before greenhouse gas-spewing industrial activities kicked into gear but still relatively recent. It was also after the unusually cold period called the Little Ice Age driven by volcanic eruptions and solar activity.

“Reframing our definition of pre-industrial to the 18th century makes a lot of scientific sense,” Nerilie Abram, one of the authors of the Nature study who was not involved with the new work, said in an email.

To figure out how much temperatures have risen since then, Ed Hawkins, a climate scientist at the University of Reading in England, and his co-authors back-calculated the temperature record using measurements of factors that affect climate, such as solar activity and volcanic eruptions,  as well as more local temperature records that extend further back in time.

RELATED 2016 Was the Hottest Year on Record
Study Suggests Earlier Onset of Human-Driven Warming
The Temperature Spiral, Now With 2016’s Record Heat

They determined that the period from 1986-2005 was likely 0.55-0.8°C (1-1.4°F) above pre-industrial levels. That’s in line with other estimates made using the late 19th century as a baseline, such as NASA, which estimates warming from the late 19th century to 1986-2005 at about 0.66°C.

This suggests that using the late 19th century baseline captures the bulk of the warming that has occurred from human activities.

Hawkins and his co-authors calculated that the amount of warming through 2016 would be about 1°C (1.8°F) above the late 19th century, and possibly slightly higher, findings in line with other estimates. 2015, the hottest year on record until it was just surpassed by 2016, was likely the first year to pass this mark, they said.

However, that 1°C is likely just a lower bound of warming, Hawkins said, with the possibility that up to another 0.2°C can be tacked on if truly comparing to a pre-industrial baseline. This difference in warming matters more if countries want to aim for the tougher 1.5°C warming limit, Hawkins said.

“It doesn’t change that big picture,” he said, “but if you’re a policymaker and you’re very serious about 1.5°C” the difference between 1°C and 1.2°C of temperature rise is much more important than it is for a limit of 2°C. (Hawkins has also developed different visualizations of this warming, including a spiral showing global temperature rise that went viral last year.)

How Close Is 1.5°C? Depends When You Measure From Central The so-called “hockey stick” graph, which shows temperatures both from the instrumental record (in red) and paleoclimate data.
Click image to enlarge. Credit: IPCC

To avoid the uncertainty inherent in any evaluation of a pre-industrial period, the authors suggest that it might make more sense to define further temperature rise from a more recent time period. Abram disagreed, saying that could “take attention away from how much damage has already been done and just how quickly we are approaching levels where the scientific evidence tells us we risk causing very dangerous climate changes.”

Gavin Schmidt, director of NASA’s Goddard Institute of Space Studies, said in an email that while the study “highlights a real issue,” the difference in baselines “really doesn’t change what one might do policy-wise, nor does it reduce future impacts of any additional CO2 emission.” Schmidt wasn’t involved in the study.

However, Michael Mann, a Penn State climate scientist who also wasn’t involved in the study, thinks that defining the pre-industrial baseline does matter. He said the findings of the new study agreed with work he has done on the subject.

“It matters, because it actually indicates that we have more work to do than we might have thought to avoid 2°C warming relative to pre-industrial, what has been defined in policy circles as ‘dangerous’

This article originally appeared on Climate Central

Related Books

Climate Change: What Everyone Needs to Know

by Joseph Romm
0190866101The essential primer on what will be the defining issue of our time, Climate Change: What Everyone Needs to Know® is a clear-eyed overview of the science, conflicts, and implications of our warming planet. From Joseph Romm, Chief Science Advisor for National Geographic's Years of Living Dangerously series and one of Rolling Stone's "100 people who are changing America," Climate Change offers user-friendly, scientifically rigorous answers to the most difficult (and commonly politicized) questions surrounding what climatologist Lonnie Thompson has deemed "a clear and present danger to civilization.". Available On Amazon

Climate Change: The Science of Global Warming and Our Energy Future second edition Edition

by Jason Smerdon
0231172834This second edition of Climate Change is an accessible and comprehensive guide to the science behind global warming. Exquisitely illustrated, the text is geared toward students at a variety of levels. Edmond A. Mathez and Jason E. Smerdon provide a broad, informative introduction to the science that underlies our understanding of the climate system and the effects of human activity on the warming of our planet.Mathez and Smerdon describe the roles that the atmosphere and ocean play in our climate, introduce the concept of radiation balance, and explain climate changes that occurred in the past. They also detail the human activities that influence the climate, such as greenhouse gas and aerosol emissions and deforestation, as well as the effects of natural phenomena.  Available On Amazon

The Science of Climate Change: A Hands-On Course

by Blair Lee, Alina Bachmann
194747300XThe Science of Climate Change: A Hands-On Course uses text and eighteen hands-on activities to explain and teach the science of global warming and climate change, how humans are responsible, and what can be done to slow or stop the rate of global warming and climate change. This book is a complete, comprehensive guide to an essential environmental topic. Subjects covered in this book include: how molecules transfer energy from the sun to warm the atmosphere, greenhouse gases, the greenhouse effect, global warming, the Industrial Revolution, the combustion reaction, feedback loops, the relationship between weather and climate, climate change, carbon sinks, extinction, carbon footprint, recycling, and alternative energy. Available On Amazon

From The Publisher:
Purchases on Amazon go to defray the cost of bringing you InnerSelf.comelf.com, MightyNatural.com, and ClimateImpactNews.com at no cost and without advertisers that track your browsing habits. Even if you click on a link but don't buy these selected products, anything else you buy in that same visit on Amazon pays us a small commission. There is no additional cost to you, so please contribute to the effort. You can also use this link to use to Amazon at any time so you can help support our efforts.

 

enafarzh-CNzh-TWnltlfrdehiiditjakomsfaptruesswsvthtrurvi

EVIDENCE

What Happens When The Permafrost Thaws?
by Official W5
Almost half of Canada sits on permanently frozen land called permafrost, but climate change is causing it to thaw and…
Annual Assessment of North Cascades Glaciers Finds Shocking Loss of Volume
Annual Assessment of North Cascades Glaciers Finds Shocking Loss of Volume
by Mauri Pelto
The summer of 2019 found the North Cascade Glacier Climate Project in the field for the 36th consecutive summer…
For The First Time, We Can Measure The Human Footprint On Antarctica
For The First Time, We Can Measure The Human Footprint On Antarctica
by Shaun Brooks and Julia Jabour
Most people picture Antarctica as a frozen continent of wilderness, but people have been living – and building – there…
The Air Above Antarctica Is Suddenly Getting Warmer
The Air Above Antarctica Is Suddenly Getting Warmer
by Harry Hendon, et al
Record warm temperatures above Antarctica over the coming weeks are likely to bring above-average spring temperatures…
How Close Is 1.5°C? Depends When You Measure From
How Close Is 1.5°C? Depends When You Measure From
Most scientists studying global warming compare today’s temperatures to those of the late 19th century because that is…
Why Methane Emissions Matter To Climate Change
Why Methane Emissions Matter To Climate Change
by Anthony J. Marchese and Dan Zimmerle
The EPA on Aug. 29 unveiled a proposal to rescind regulations to limit methane emissions from the oil and gas industry.
French wines show hot dry years are now normal
French Wines Show Hot Dry Years Are Now Normal
by Tim Radford
Records have begun to topple for the world’s finest tipple. French wines can now count 664 years of vintage information…
The Amazon Fire Crisis Has Been 500 Years In The Making – As Brazil's Indigenous People Know Only Too Well
The Amazon Fire Crisis Has Been 500 Years In The Making – As Brazil's Indigenous People Know Only Too Well
by Darren Reid
São Paulo – the largest city in the Americas – was recently plunged into darkness in the middle of the day due to smoke…

LATEST VIDEOS

Bill Nye And The Climate Crisis
by MSNBC
On a special show before a live studio audience, Bill Nye the science guy discusses the climate crisis with Chris Hayes.
How Greenland's Massive Ice Melt Will Totally Transform The World
by Channel 4 News
Remember that heatwave back in August? Well, the Arctic remembers it too. Record rates of ice melt have been recorded…
China Is Positioned To Lead On Climate Change As The US Rolls Back Its Policies
China Is Positioned To Lead On Climate Change As The US Rolls Back Its Policies
by Kelly Sims Gallagher and Fang Zhang
As the effects of climate change become more widespread and alarming, U.N. Secretary-General António Guterres has…
What Happens When The Permafrost Thaws?
by Official W5
Almost half of Canada sits on permanently frozen land called permafrost, but climate change is causing it to thaw and…
We Are Striking to Disrupt the System: An Hour with 16-Year-Old Climate Activist Greta Thunberg
by Democracy Now!
In her first extended broadcast interview in the United States, we spend the hour with Greta Thunberg, the 16-year-old…
Annual Assessment of North Cascades Glaciers Finds Shocking Loss of Volume
Annual Assessment of North Cascades Glaciers Finds Shocking Loss of Volume
by Mauri Pelto
The summer of 2019 found the North Cascade Glacier Climate Project in the field for the 36th consecutive summer…
Breakdown In Coral Reef Iconic Spawning Puts Species At Risk Of Extinction
Breakdown In Coral Reef Iconic Spawning Puts Species At Risk Of Extinction
by Heidi Burdett
Breakdown In Coral Reef Iconic Spawning Puts Species At Risk Of Extinction
How Climate Change Is Driving Emigration From Central America
How Climate Change Is Driving Emigration From Central America
by Miranda Cady Hallett
Clouds of dust rose behind the wheels of the pickup truck as we hurtled over the back road in Palo Verde, El Salvador.

LATEST ARTICLES

Bill Nye And The Climate Crisis
by MSNBC
On a special show before a live studio audience, Bill Nye the science guy discusses the climate crisis with Chris Hayes.
Roiled By Trump Politics, NOAA Seeks Accountability, Atonement
by MSNBC
Rachel Maddow reports on the backlash within the weather science community over an unsigned statement from NOAA…
Extreme Cities: Ground Zero for Climate Change
by The Laura Flanders Show
No matter how we tackle climate change, cities are key.
How Greenland's Massive Ice Melt Will Totally Transform The World
by Channel 4 News
Remember that heatwave back in August? Well, the Arctic remembers it too. Record rates of ice melt have been recorded…
China Is Positioned To Lead On Climate Change As The US Rolls Back Its Policies
China Is Positioned To Lead On Climate Change As The US Rolls Back Its Policies
by Kelly Sims Gallagher and Fang Zhang
As the effects of climate change become more widespread and alarming, U.N. Secretary-General António Guterres has…
We Need More Carbon In Our Soil To Help Australian Farmers Through The Drought
We Need More Carbon In Our Soil To Help Australian Farmers Through The Drought
by Nanthi Bolan
Australia has never been a stranger to droughts, but climate change is now super-charging them.
Climate Breakdown Is Pushing Brazil's Iconic Araucaria Tree To Extinction
Climate Breakdown Is Pushing Brazil's Iconic Araucaria Tree To Extinction
by Oliver Wilson
For hundreds of thousands of years, the distinctive candelabra shapes of Araucaria trees (Araucaria angustifolia) have…
What Happens When The Permafrost Thaws?
by Official W5
Almost half of Canada sits on permanently frozen land called permafrost, but climate change is causing it to thaw and…