No, you can’t argue the Medieval warm period is evidence that today’s climate change isn’t all that bad

23 04 2021
As this reconstructed village shows, Vikings made it as far as Newfoundland during the Medieval warm period. Wikimedia/Dylan Kereluk, CC BY-SA


Frédérik Saltré, Flinders University and Corey J. A. Bradshaw, Flinders University


What was the Medieval warm period? What caused it, and did carbon dioxide play a role?

We are living in a world that is getting warmer year by year, threatening our environment and way of life.

But what if these climate conditions were not exceptional? What if it had already happened in the past when human influences were not part of the picture?

The often mentioned Medieval warm period seems to fit the bill. This evokes the idea that if natural global warming and all its effects occurred in the past without humans causing them, then perhaps we are not responsible for this one. And it does not really matter because if we survived one in the past, then we can surely survive one now.

But it’s just not that simple.


Read more: 2,000 years of records show it’s getting hotter, faster


The Medieval climate anomaly

This Medieval period of warming, also known as the Medieval climate anomaly, was associated with an unusual temperature rise roughly between 750 and 1350 AD (the European Middle Ages). The available evidence suggests that at times, some regions experienced temperatures exceeding those recorded during the period between 1960 and 1990. Read the rest of this entry »





Citizens ask the experts in climate-change communication

7 02 2021

In the second of two consecutive interviews with climate-change experts (see the first one here), readers of the Spanish magazine Quercus have a chat with Katharine Hayhoe. Her words blend hope with the most putrid reality of economics and politics. May this interview inspire some environment-friendly changes in our daily routines and in how we see the beautiful life that surrounds us.


PhD in climate science, professor in political science and co-director of the Climate Centre at Texas Tech University (USA), Katharine Hayhoe works on climate projections and mitigation (1-3). Her prominent profile as communicator (4-6) made her one of the 100th most influential people in the world. To the left, Katharine has “A conversation on climate change” with citizens at the Lyndon Baines Johnson Presidential Library and Museum (Austin). Photo credits: Artie Limmer (portrait) & Jay Godwin (talk).


Interview done 20 October 2020

Below we italicise each question and the name of the person asking the question and cite a range of publications we deem relevant per question. For expanding on Katharyne Hayhoe’s views on climate change, see a sample of her public talks here and here, interviews here and here, and newspaper articles here and here. We love one of the titles of her newspaper articles “A thermometer is not liberal or conservative”. A spanish version of this article and interview has been published in the February 2021 issue of the magazine Quercus.


Question 1 of 4: There are extraordinarily influential people on a global scale who have a utilitarian perspective of nature, and think that climate change (be it of anthropogenic origin or not) entails advantages and opportunities to Western economies, and that we will be able to adapt whether changes are reversible or irreversible. Can we engage or use those influential people in any possible way to abate climate change? (7, 8) Iñaki García Pascual (Environmental geologist)

Hayhoe:

Climate change has some localised, short-term, specific benefits (9). One example is increased access to oil and gas resources in a melting Arctic (10). This temporarily profits oil and gas industries, provides some financial benefit to local communities in Greenland and Alaska short-term, and harms both them and everyone else in the long term. A book called Windfall by Mackenzie Funk describes who is “profiteering” from climate change, and how. 

Overall, however, climate change already harms the majority of people today. The poor, the vulnerable, and the marginalized are affected first and foremost. Since the 1960s, for example, climate change has increased the gap between the richest and poorest countries in the world by as much as 25 per cent. In 2019, UN Special Rapporteur on extreme poverty and human rights, Philip Alston, warned that climate change “threatens to undo the last 50 years” of development, global health and poverty reduction.” (11)

And while the rich may be able to temporarily “buy their way out of rising heat and hunger”, as Alston put it, the truth is that we all live on this planet, no matter how wealthy and influential we are. The air we breathe, the water we drink, the food we eat and all the resources we use come from our shared home. 

Climate change threatens the ability of our planet to support human civilisation as we know it. It is a threat multiplier, attacking our health, our economy, our resources and even our security. As climate change intensifies and economic markets crumble and refugee crises surge, even those who may temporarily benefit from a warmer world will be negatively impacted by these changes long-term.

That’s why it makes so much sense to take practical steps to limit carbon pollution now. Many of these actions also provide us with short-term benefits that can be quantified in economic terms: like energy savings through efficiency, cheaper electricity from renewables, more jobs, better public transportation, and even faster cars (like Tesla). Climate action also provides less tangible but arguably even more important benefits: cleaner air and water, better health, poverty reduction, and a host of other co-benefits that substantively move us towards meeting key UN Sustainable Development Goals.

To care about climate change, we don’t have to be a certain type of person or live in a certain place or vote a certain way: all we have to be is a human living on this planet, and we’re all that.

Read the rest of this entry »




Worried about Earth’s future? Well, the outlook is worse than even scientists can grasp

14 01 2021

Daniel Mariuz/AAP

Corey J. A. Bradshaw, Flinders University; Daniel T. Blumstein, University of California, Los Angeles, and Paul Ehrlich, Stanford University

Anyone with even a passing interest in the global environment knows all is not well. But just how bad is the situation? Our new paper shows the outlook for life on Earth is more dire than is generally understood.

The research published today reviews more than 150 studies to produce a stark summary of the state of the natural world. We outline the likely future trends in biodiversity decline, mass extinction, climate disruption and planetary toxification. We clarify the gravity of the human predicament and provide a timely snapshot of the crises that must be addressed now.

The problems, all tied to human consumption and population growth, will almost certainly worsen over coming decades. The damage will be felt for centuries and threatens the survival of all species, including our own.

Our paper was authored by 17 leading scientists, including those from Flinders University, Stanford University and the University of California, Los Angeles. Our message might not be popular, and indeed is frightening. But scientists must be candid and accurate if humanity is to understand the enormity of the challenges we face.

Girl in breathing mask attached ot plant in container

Humanity must come to terms with the future we and future generations face. Shutterstock

Getting to grips with the problem

First, we reviewed the extent to which experts grasp the scale of the threats to the biosphere and its lifeforms, including humanity. Alarmingly, the research shows future environmental conditions will be far more dangerous than experts currently believe. Read the rest of this entry »





Time for a ‘cold shower’ about our ability to avoid a ghastly future

13 01 2021

I wish it need not have happened in my time,” said Frodo. “So do I,’ said Gandalf, “and so do all who live to see such times. But that is not for them to decide. All we have to decide is what to do with the time that is given us.”

Frodo Baggins and Gandalf, The Fellowship of the Ring

Today, 16 high-profile scientists and I published what I describe as a ‘cold shower’ about society’s capacity to avoid a ghastly future of warfare, disease, inequality, persecution, extinction, and suffering.

And it goes way beyond just the plight of biodiversity.

No one who knows me well would mistake me for an optimist, try as I might to use my colleagues’ and my research for good. Instead, I like to describe myself as a ‘realist’. However, this latest paper has made even my gloomier past outputs look downright hopeful.

And before being accused of sensationalism, let me make one thing abundantly clear — I sincerely hope that what we describe in this paper does not come to pass. Not even I am that masochistic.

I am also supportive of every attempt to make the world a better place, to sing about our successes, regroup effectively from our failures, and maintain hope in spite of evidence to the contrary.

But failing to acknowledge the magnitude and the gravity of the problems facing us is not just naïve, it is positively dangerous and potentially fatal.

It is this reason alone that prompted us to write our new paper “Underestimating the challenges of
avoiding a ghastly future
” just published in the new journal, Frontiers in Conservation Science.

Read the rest of this entry »




Citizens ask the expert in climate physics

24 11 2020

In the first of two consecutive interviews with climate-change experts, authors, editors and readers of the Spanish magazine Quercus have a chat with Ken Caldeira, a global-ecology researcher at the Carnegie Institution for Science (Washington, USA). His responses attest that the climate system is complex, and that we need to be practical in dealing with the planet’s ongoing climate emergency.

PhD in atmospheric sciences and professor at Stanford University (USA), Ken Caldeira has pioneered the study of ocean acidification and its impact on coral reefs (1) and geoengineering solutions to mitigate anthropogenic climate change by extracting carbon from the atmosphere and reflecting solar radiation (2, 3). He has also been part of the Intergovernmental Panel on Climate change (IPCC) and assessed zero-emissions scenarios (4, 5). To the right, Ken manoeuvers a drone while collecting aerial data from the Great Barrier Reef in Australia (6). Source.

SARS-Covid-19 is impacting the world. In our home country, Spain, scientists argue that (i) previous budget cuts in public health have weakened our capacity to tackle the pandemic (7), and (ii) the expert panels providing advice to our government should be independent of political agendas in their membership and decisions (8). Nevertheless, the Spanish national and regional governments’ data lack the periodicity, coherence, and detail to harness an effective medical response (9). Sometimes it feels as if politics partly operate by neglecting the science needed to tackle challenges such as the covid pandemic or climate change.

Having said that, even if a country has cultivated and invested in the best science possible, people have difficulties coming to terms with the idea that scientists work with probabilities of alternative scenarios. As much as there are different ways of managing a pandemic, scientists differ about how to mitigate the ecological, economic, and health impacts of a high-carbon society.

Thus, a more and more common approach is to make collective assessments (elicitations) by weighing different points of view across experts — for instance, to establish links between climate change and armed conflict (10) or to evaluate the role of nuclear energy as we transition to a low-carbon energy-production model (11). The overarching goal is to quantify consensus based on different (evidence-based) opinions.

The questions we here ask Ken Caldeira could well have different answers if asked of other experts. Still, as Ken points out, it is urgent that (of the many options available) we use the immense and certainty-proof knowledge we have already about climate change to take actions that work.

Interview done 23 January 2020 

We italicise each question and the name of the person asking the question and cite one to three relevant publications per question. For expanding on Ken Caldeira’s views on climate change, see a sample of his public talks here and here and newspaper articles here and here.

Read the rest of this entry »





Cartoon guide to biodiversity loss LXIII

26 10 2020

The sixth set of biodiversity cartoons for 2020. See full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here.


Read the rest of this entry »





Climate explained: humans have dealt with plenty of climate variability

23 09 2020
© Professor John Long, Flinders University, Author provided


(originally published on The Conversation)


 

How much climate variability have humans dealt with since we evolved and since we started settling (Neolithic times)? How important was migration to human survival during these periods?

 

The climate always fluctuates as variation in the Sun’s heat reaching Earth drives glacial-interglacial cycles. Over the past 420,000 years there have been at least four major transitions between ice ages and relatively warmer interglacial periods.

Modern humans emigrated from Africa to populate the rest of the globe between 120,000 and 80,000 years ago, which means our species has had to adapt to many massive climate transitions.

 

Warming and cooling

The Last Interglacial 129,000–116,000 years ago was a period of intense global warming (from around 2 ℃ higher than today to as much as 11 ℃ higher in the Arctic), leading to a large reduction of the Arctic, Greenland and Antarctic ice sheets, and a 6–9 m rise in sea level.

The front of a glacier breaking away and falling into the sea.
Arctic glaciers have melted before. Flickr/Kimberly Vardeman, CC BY

The Last Glacial Maximum from 26,500–19,000 years ago coincided with a large drop in atmospheric CO₂ and a 4.3 ℃ cooling globally.


Read more: Climate explained: will the tropics eventually become uninhabitable?


 

Low temperatures turned much of the world’s water into ice and expanded glaciers.

Read the rest of this entry »




Many animals won’t cope with climate change without access to ample drinking water

12 08 2020

Climate change implies change in temperature and water, and both factors shape species’ tolerances to thermal stress. In our latest article, we show that lack of drinking water maximises differences in tolerance to high temperatures among populations of Iberian lizard species.

drinking

Climate change is a multidimensional phenomenon comprising temporal and spatial shifts in both temperature and precipitation (1). How we perceive climate change depends on whether we measure it as shift in (i) mean conditions (e.g., the mean air temperature or rainfall over a decade within a given territory), (ii) magnitude or frequency of extreme conditions (e.g., the frequency of floods or tornados or the number of days with temperatures or rainfall above or below a given threshold), or (iii) speed at which mean or extreme conditions change in space and/or time.

In aquatic ecosystems, climate change further alters water acidity, oxygen dissolution and melting of ice. However, many people, including some scientists, tend to equate climate change erroneously with increased mean temperatures. Psychologists have made the semantic point that the use of the expressions climate change and global warming as synonyms can give mixed messages to politicians, and society in general, about how serious and complex the climate emergency we are facing really is (2, 3) — see NASA’s simple-worded account on the subject here.

In our latest article (4), we reviewed the ecological literature to determine to what extent ecologists investigating the tolerance of terrestrial animals to high temperatures have looked at thermal effects over water effects. It turns out, they were five times more likely to examine temperature over water.

cb_BAAE_WaterLizardsNetwork

Frequency of correlations between climate (air temperature versus precipitation) and tolerance to high temperature of terrestrial fauna in 64 papers published in the ecological literature (thickest link = 36, thinnest link = 2) following a systematic literature review in Scopus (4).

This is counterintuitive. Just imagine you have been walking under the sun for several hours on one of those dog days of summer, and you are offered to choose between a sunshade or a bottle of water. I’d bet you’d choose the bottle of water.

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Successful movers responding to climate change

16 06 2020

tropical fishes range shiftsEcologists often rely on measuring certain elements of a species’ characteristics, behaviour, or morphology to determine if these — what we call ‘traits’ — give them certain capacities to exploit their natural environments. While sometimes a bit arbitrarily defined, the traits that can be measured are many indeed, and sometimes they reveal rather interesting elements of a species’ resilience in the face of environmental change.

As we know, climate change is changing the way species are distributed around the planet, for the main (and highly simplified) reason that the environments in which they’ve evolved and to which they have adapted are changing.

In the simplest case, a warming climate means that there is a higher and higher chance you’ll experience temperatures that really don’t suit you that well (think of a koala or a flying fox baking in a tree when the thermometer reads +45° in the shade). Just like you seeking those nice, air-conditioned spaces on a scorcher of a day, species like to move to where conditions are more acceptable to their particular physiologies and behaviours.

When they can’t change fast enough, they go extinct.

Ecologists use life-history traits to predict which species have the highest probability of moving to new areas in response to climate change. Most studies into this phenomenon have largely ignored that range shifts in fact occur in sequential stages: (1) the species arrives in a new place for the first time, (2) its population increases in size (and extent), and (3) it can continue to persist in the new spot. Read the rest of this entry »





Cartoon guide to biodiversity loss LXI

31 05 2020

The fourth set of biodiversity cartoons for 2020. See full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here.


Read the rest of this entry »





Cartoon guide to biodiversity loss LX

8 04 2020

The third set of biodiversity cartoons for 2020 (plus a video treat). See full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here.


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A plant’s adaptive traits don’t follow climate conditions as you might expect

27 03 2020

mountain

Just a quick post today, my last one for March. Like probably most of you, I’ve been trying to pretend to be as normal as possible despite the COVID-19 surrealism all around me. But even COVID-19 has shifted my research to a small degree.

But I’m not going to talk about the global pandemic right now (I can almost hear the collective sigh of relief). Instead, I’m going to go back to topic and discuss a paper that I’ve just co-authored.

Last year I went to China’s Yunnan Province where I met some fantastic colleagues at the Xishuangbanna Tropical Botanical Garden who were doing some very cool stuff with the variation in plant functional traits across environmental gradients.

Well, those colleagues invited me to participate in one those research projects, and I’m happy to say that the result has just been published in Forests.

Measuring the functional traits of different alpine trees species in the Changbai Mountains of far north-eastern China (no, I didn’t get to go there), the research set out to test how these varied among species and elevation.

Of course, one expects that different trees use different combinations of traits to survive the rigours of mountain life (high variation in temperature, freezing, wind, etc.), but generally speaking, you might expect things like xylem vessel diameter and density to change more or less monotonically (i.e., changing in a consistent manner as elevation rises or falls). This is because trees should adapt their traits to the local conditions as best they can. Read the rest of this entry »





Cartoon guide to biodiversity loss LIX

24 02 2020

The second set of six biodiversity cartoons for 2020. See full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here.


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Heat tolerance highly variable among populations and species

14 01 2020

Many ecological studies have examined the tolerance of terrestrial wildlife to high and low air temperatures over global scales (e.g., 1, 2, 3). This topic has been boosted in the last two decades by ongoing and predicted impacts of climate change on biodiversity (see summary of 2019 United Nation’s report here and here).

However, it is unfortunate that for most species, studies have measured thermal tolerance from a single location or population. Researchers interested in global patterns of thermal stress collect those measurements from the literature for hundreds to thousands of species [recently compiled in the GlobTherm database] (4), and are therefore often restricted to analysing one value of thermal tolerance per species.

CB_FunctionalEcology_jan2020_Photo

Three of the 15 species of Iberian lacertids sampled in our study of thermal tolerance (9), including the populations of Algerian psammodromus (Psammodromus algirus), Geniez’s wall lizard (Podarcis virescens) and Western green lizard (Lacerta bilineata) sampled in Navacerrada (Madrid), Fuertescusa (Cuenca) and Moncayo (Soria), respectively. Photos by S. Herrando-Pérez

Using this approach, ecologists have concluded that cold tolerance is far more variable than heat tolerance across species from the tropics to the boreal zone (5-8). Consequently, tolerance to heat stress might be a species trait with limited potential to change in response to global warming compared to cold tolerance (5). Read the rest of this entry »





Cartoon guide to biodiversity loss LVIII

4 01 2020

The first set of six biodiversity cartoons for 2020. This special, Australia-is-burning-down-themed set is dedicated to Scott Morrison and his ilk. See full stock of previous ‘Cartoon guide to biodiversity loss’ compendia here.


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Influential conservation ecology papers of 2019

24 12 2019

Bradshaw-Waves breaking on rocks Macquarie Island
As I’ve done for the last six years, I am publishing a retrospective list of the ‘top’ 20 influential papers of 2019 as assessed by experts in F1000 Prime (in no particular order). See previous years’ lists here: 20182017, 20162015, 2014, and 2013.

Read the rest of this entry »





Did people or climate kill off the megafauna? Actually, it was both

10 12 2019

When freshwater dried up, so did many megafauna species.
Centre of Excellence for Australian Biodiversity and Heritage, Author provided

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Earth is now firmly in the grips of its sixth “mass extinction event”, and it’s mainly our fault. But the modern era is definitely not the first time humans have been implicated in the extinction of a wide range of species.

In fact, starting about 60,000 years ago, many of the world’s largest animals disappeared forever. These “megafauna” were first lost in Sahul, the supercontinent formed by Australia and New Guinea during periods of low sea level.

The causes of these extinctions have been debated for decades. Possible culprits include climate change, hunting or habitat modification by the ancestors of Aboriginal people, or a combination of the two.


Read more: What is a ‘mass extinction’ and are we in one now?


The main way to investigate this question is to build timelines of major events: when species went extinct, when people arrived, and when the climate changed. This approach relies on using dated fossils from extinct species to estimate when they went extinct, and archaeological evidence to determine when people arrived.


Read more: An incredible journey: the first people to arrive in Australia came in large numbers, and on purpose


Comparing these timelines allows us to deduce the likely windows of coexistence between megafauna and people.

We can also compare this window of coexistence to long-term models of climate variation, to see whether the extinctions coincided with or shortly followed abrupt climate shifts.

Data drought

One problem with this approach is the scarcity of reliable data due to the extreme rarity of a dead animal being fossilised, and the low probability of archaeological evidence being preserved in Australia’s harsh conditions. Read the rest of this entry »





Climate change and humans together pushed Australia’s biggest beasts to extinction

25 11 2019

people-megafaunaOver the last 60,000 years, many of the world’s largest species disappeared forever. Some of the largest that we generally call ‘megafauna’ were first lost in Sahul — the super-continent formed by the connection of Australia and New Guinea during periods of low sea level. The causes of these extinctions have been heavily debated for decades within the scientific community.

Three potential drivers of these extinctions have been suggested. The first is climate change that assumes an increase in arid conditions that eventually became lethal to megafauna. The second proposed mechanism is that the early ancestors of Aboriginal people who either hunted megafauna species to extinction, or modified ecosystems to put the largest species at a disadvantage. The third and most nuanced proposed driver of extinction is the combination of the first two.

The primary scientific tools we scientists use to determine which of these proposed causes of extinction have the most support are dated fossil records from the extinct species themselves, as well as archaeological evidence from early Aboriginal people. Traditionally, the main way we use these data is to construct a timeline of when the last fossil of a species was preserved, and compare this to evidence indicating when people arrived. We can also reconstruct climate patterns back tens of thousands of years using models similar to the ones used today to predict future climates. Based on the comparison of all of these different timelines, we conclude that abrupt climate changes in the past were influential if they occurred at or immediately before a recorded extinction event. On the other hand, if megafauna extinctions occur immediately after humans are thought to have arrived, we attribute more weight to human arrival as a driver.

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What is a ‘mass extinction’ and are we in one now?

13 11 2019

(reproduced from The Conversation)

For more than 3.5 billion years, living organisms have thrived, multiplied and diversified to occupy every ecosystem on Earth. The flip side to this explosion of new species is that species extinctions have also always been part of the evolutionary life cycle.

But these two processes are not always in step. When the loss of species rapidly outpaces the formation of new species, this balance can be tipped enough to elicit what are known as “mass extinction” events.


Read more: Climate change is killing off Earth’s little creatures


A mass extinction is usually defined as a loss of about three quarters of all species in existence across the entire Earth over a “short” geological period of time. Given the vast amount of time since life first evolved on the planet, “short” is defined as anything less than 2.8 million years.

Since at least the Cambrian period that began around 540 million years ago when the diversity of life first exploded into a vast array of forms, only five extinction events have definitively met these mass-extinction criteria.

These so-called “Big Five” have become part of the scientific benchmark to determine whether human beings have today created the conditions for a sixth mass extinction.

An ammonite fossil found on the Jurassic Coast in Devon. The fossil record can help us estimate prehistoric extinction rates. Corey Bradshaw, Author provided

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Koala extinctions past, present, and future

12 06 2019

Koala

Photo by John Llewelyn

Koalas are one of the most recognised symbols of Australian wildlife. But the tree-living marsupial koala is not doing well throughout much of its range in eastern Australia. Ranging as far north as Cairns in Queensland, to as far west as Kangaroo Island in South Australia, the koala’s biggest threats today are undeniably deforestation, road kill, dog attacks, disease, and climate change.

With increasing drought, heatwaves, and fire intensity and frequency arising from the climate emergency, it is likely that koala populations and habitats will continue to decline throughout most of their current range.

But what was the distribution of koalas before humans arrived in Australia? Were they always a zoological feature of only the eastern regions?

The answer is a resounding ‘no’ — the fossil record reveal a much more complicated story.

Read the rest of this entry »