Climate change and wildfires – how do we know if there is a link?



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A firefighter runs after trying to save a home in Lakeport, California, suffering its biggest fires ever.
AP Photo/Noah Berger

Kevin Trenberth, National Center for Atmospheric Research

Once again, the summer of 2018 in the Northern Hemisphere has brought us an epidemic of major wildfires.

These burn forests, houses and other structures, displace thousands of people and animals, and cause major disruptions in people’s lives. The huge burden of simply firefighting has become a year-round task costing billions of dollars, let alone the cost of the destruction. The smoke veil can extend hundreds or even thousands of miles, affecting air quality and visibility. To many people, it has become very clear that human-induced climate change plays a major role by greatly increasing the risk of wildfire.

Yet it seems the role of climate change is seldom mentioned in many or even most news stories about the multitude of fires and heat waves. In part this is because the issue of attribution is not usually clear. The argument is that there have always been wildfires, and how can we attribute any particular wildfire to climate change?

As a climate scientist, I can say this is the wrong framing of the problem. Global warming does not cause wildfires. The proximate cause is often human carelessness (cigarette butts, camp fires not extinguished properly, etc.), or natural, from “dry lightning” whereby a thunderstorm produces lightning but little rain. Rather, global warming exacerbates the conditions and raises the risk of wildfire.

Even so, there is huge complexity and variability from one fire to the next, and hence the attribution can become complex. Instead, the way to think about this is from the standpoint of basic science – in this case, physics.

This year is proving to be another active wildfire season.
Climate Central, CC BY-NC

Global warming is happening

To understand the interplay between global warming and wildfires, consider what’s happening to our planet.

The composition of the atmosphere is changing from human activities: There has been over a 40 percent increase in carbon dioxide, mainly from fossil fuel burning since the 1800s, and over half of the increase is since 1985. Other heat-trapping gases (methane, nitrous oxide, etc.) are also increasing in concentration in the atmosphere from human activities. The rates are accelerating, not declining (as hoped for with the Paris agreement).

This leads to an energy imbalance for the planet.

The flows of energy through the climate system are schematically illustrated with numbers on the top-of-atmosphere values and net energy imbalance at the surface.
Trenberth et al 2009

Heat-trapping gases in the atmosphere act as a blanket and inhibit the infrared radiation – that is, heat from the Earth – from escaping back into space to offset the continual radiation coming from the sun. As these gases build up, more of this energy, mostly in the form of heat, remains in our atmosphere. The energy raises the temperature of the land, oceans and atmosphere, melts ice, thaws permafrost, and fuels the water cycle through evaporation.

Moreover, we can estimate Earth’s energy imbalance quite well: It amounts to about 1 watt per square meter, or about 500 terawatts globally.

While this factor is small compared with the natural flow of energy through the system, which is 240 watts per square meter, it is large compared with all other direct effects of human activities. For instance, the electrical power generation in the U.S. last year averaged 0.46 terawatts.

The extra heat is always the same sign and it is spread across the globe. Accordingly, where this energy accumulates matters.

Tracking the Earth’s energy imbalance

The heat mostly accumulates ultimately in the ocean – over 90 percent. This added heat means the ocean expands and sea level rises.

Heat also accumulates in melting ice, causing melting Arctic sea ice and glacier losses in Greenland and Antarctica. This adds water to the ocean, and so the sea level rises from this as well, rising at a rate of over 3 milimeters year, or over a foot per century.

Global ocean heat content for the top 2000 meters of the ocean, with uncertainty estimates by the pink region.
ScienceAdvances, CC BY-NC

On land, the effects of the energy imbalance are complicated by water. If water is present, the heat mainly goes into evaporation and drying, and that feeds moisture into storms, which produce heavier rain. But the effects do not accumulate provided that it rains on and off.

However, in a dry spell or drought, the heat accumulates. Firstly, it dries things out, and then secondly it raises temperatures. Of course, “it never rains in southern California” according to the 1970s pop song, at least in the summer half year.

So water acts as the air conditioner of the planet. In the absence of water, the excess heat effects accumulate on land both by drying everything out and wilting plants, and by raising temperatures. In turn, this leads to heat waves and increased risk of wildfire. These factors apply in regions in the western U.S. and in regions with Mediterranean climates. Indeed many of the recent wildfires have occurred not only in the West in the United States, but also in Portugal, Spain, Greece, and other parts of the Mediterranean.

A satellite image of the Carr Fire in California. Drought conditions, in addition to a lot of dead trees and vegetation, are contributing to another year of severe wildfires.
NASA

The conditions can also develop in other parts of the world when strong high pressure weather domes (anticyclones) stagnate, as can happen in part by chance, or with increased odds in some weather patterns such as those established by either La Niña or El Niño events (in different places). It is expected that these dry spots move around from year to year, but that their abundance increases over time, as is clearly happening.

How big is the energy imbalance effect over land? Well, 1 Watt per square meter over a month, if accumulated, is equivalent to 720 Watts per square meter over one hour. 720 Watts is equivalent to full power in a small microwave oven. One square meter is about 10 square feet. Hence, after one month this is equivalent to: one microwave oven at full power every square foot for six minutes. No wonder things catch on fire!

Attribution science

Coming back to the original question of wildfires and global warming, this explains the argument: there is extra heat available from climate change and the above indicates just how large it is.

In reality there is moisture in the soil, and plants have root systems that tap soil moisture and delay the effects before they begin to wilt, so that it typically takes over two months for the effects to be large enough to fully set the stage for wildfires. On a day to day basis, the effect is small enough to be lost in the normal weather variability. But after a dry spell of over a month, the risk is noticeably higher. And of course the global mean surface temperature is also going up.

“We can’t attribute a single event to climate change” has been a mantra of climate scientists for a long time. It has recently changed, however.

As in the wildfires example, there has been a realization that climate scientists may be able to make useful statements by assuming that the weather events themselves are relatively unaffected by climate change. This is a good assumption.

Also, climate scientists cannot say that extreme events are due to global warming, because that is a poorly posed question. However, we can say it is highly likely that they would not have had such extreme impacts without global warming. Indeed, all weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be.

The ConversationIn particular, by focusing on Earth’s Energy Imbalance, new research is expected to advance the understanding of what is happening, and why, and what it implies for the future.

Kevin Trenberth, Distinguished Senior Scientist, National Center for Atmospheric Research

This article was originally published on The Conversation. Read the original article.

Why we need some perspective on landscape photography in the Instagram age



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Bardal, from Norwegian Sublime, Ellen Marie Saethre-McGuirk, 2018.
Ellen Marie Saethre-McGuirk

Ellen Marie Saethre-McGuirk, Queensland University of Technology

Thanks to the increasing accessibility of technology, many of us will try to capture the grandeur of the natural world with our phone cameras. One of the attractions is sharing images on social media and publicly staking our claim to that experience.

A quick glance at Instagram hashtags reveals over 90 million photos tagged #landscape, around 50 million #sunrise photos and over 180 million tagged #sunset. There are 40 million #trees, nearly 90 million #clouds and about 190 million #beach photos.

But our use of platforms such as Instagram is not only changing our relationship to nature (some people have even died taking selfies in perilous places), it is also changing how we frame and experience nature.

Earlier this year a man died falling off rocks in Western Australia in the pursuit of an image. And in July three social media personalities died after falling off a Canadian waterfall.

While such deaths are rare, many travellers and adventure seekers seem to be drawn towards more remote experiences of nature in lieu of the downtrodden tourist track, using Instagram as a source for visually inspiring and enticing sites. Police warn people to avoid an imminently crumbling cliff in New South Wales, while amateur photographers continue to ignore signs and fences.




Read more:
The deadly selfie game – the thrill to end all thrills


Just as nature can harm people, people can harm nature. Two of the social media personalities who died in Canada had spent a week in jail for violating US national park regulations. In Tasmania, professional photographers have warned of the damage that could be done to the environment by hordes of people chasing views they have seen on social media. And in Esperance, Western Australia, people are trying to figure out how to capitalise on an influx of visitors driven by its discovery by Instagram users.

As part of my research, I have looked at how we present experiences of nature through new technology and social media. Most photos share traits we might describe as “a social media aesthetic”. Think of leafy paths, mountain vistas, sunrises and sunsets – often with filters or the same kinds of photo composition.

Svalbard, from Norwegian Sublime, Ellen Marie Saethre-McGuirk, 2018.
Ellen Marie Saethre-McGuirk

In my art-as-research project, the exhibition Norwegian Sublime, I used these “Instagram standards” to take photos at different locations in Norway, both well-known places such as Svalbard and less famous islands like Tomma of the Helgeland archipelago. Although they seem remote and difficult to get to, I deliberately chose places that were frequently visited and where tourism was controlled, as well as places that were literally right next to main thoroughfares, showing how the perfect picture of untouched mountain solitude can be at anyone’s fingertips. In fact, those less exotic sites around you might actually hide some of the most striking nature.

No location, from Norwegian Sublime, Ellen Marie Saethre-McGuirk, 2018.
Ellen Marie Saethre-McGuirk

Together, the images link up art photography and the history of photography with diminutive tell-tale signs typical of iPhone and social media photography. I framed clouds with Instagram squares, referencing art photography and weather studies from the early 1900s. I gave aerial photography a contemporary twist by taking photos from the window of today’s commercial flights, forever shuttling tourists back and forth.

No location, from Norwegian Sublime, Ellen Marie Saethre-McGuirk, 2018.
Ellen Marie Saethre-McGuirk

In other photos, I left those patches of surfaces that are difficult to photograph with a phone, such as reflective, wet leaves and shiny rocks, washed out and bleak. And even in the seemingly romantically remote locations I intentionally left speckled signs of people in the frame.

Voksenkollen, from Norwegian Sublime, Ellen Marie Saethre-McGuirk, 2018.
Ellen Marie Saethre-McGuirk

Landscape photography is a diverse genre, encompassing a wide range of contemporary practice. Yet, for many, iconic figures such as American photographer Ansel Adams embody what landscape photography is. His technically advanced images of the grandeur of nature are perfectly framed snapshots of near-other-worldly, untouched environments.

The Tetons and the Snake River, Ansel Adams, 1942.
Wikimedia

In a similar way, when we share landscape photos on Instagram, we often seek to show the beautiful, the staged, or the perfectly composed. We applaud these images, through liking and sharing them. And, conceivably, we increasingly picture nature as a similarly idealised aesthetic experience. We end up with very little visual diversity in how we present – and chose to experience – nature.

Tomma, from Norwegian Sublime, Ellen Marie Saethre-McGuirk, 2018.
Ellen Marie Saethre-McGuirk

Instagram ultimately boils down to two people – the one who took the picture and the viewer. Perhaps it’s time for us as Instagram photographers to think a bit more deeply about the less exotic, but no less enchanting, places around us. We should challenge what we take photos of, and how we present nature. Nature, after all, is more than #trees and #clouds.

The ConversationAnd, as Instagram viewers, we should think carefully about how we encourage different experiences of nature. Should we “like” the images and follow people and groups who clearly are pushing limits to both their own safety and the environment? Instagram is a fantastic social media tool to share the world – but it’s clear we need some perspective in using it.

Ellen Marie Saethre-McGuirk, Visiting Fellow (Assoc. Prof. Nord Univeristy), Queensland University of Technology

This article was originally published on The Conversation. Read the original article.