Dark colours play a crucial role in regulating temperatures in many biological systems. This is particularly common for animals like reptiles, which rely on environmental sources of heat to keep themselves warm.
Darker colours absorb more heat from sunlight, and animals with these colours are more commonly found in colder climates with less sunlight. This broad pattern is known as Bogert’s rule.
Birds’ eggs are useful for studying this pattern because the developing embryo can only survive in a narrow range of temperatures. But eggs cannot regulate their own temperature and, in most cases, the parent does it by sitting atop the clutch of eggs.
In colder environments, where the risk of predators is lower and the risk of chilling in cold temperatures is greater, parents spend less time away from the nest.
We predicted that if eggshell colour does play an important role in regulating the temperature of the embryo, birds living in colder environments should have darker eggs.
To test the prediction, we measured eggshell brightness and colour for 634 species of birds. That’s more than 5% of all bird species, representing 36 of the 40 large groups of species called orders.
We mapped these within each species’ breeding range and found that eggs in the coldest environments (those with the least sunlight) were significantly darker. This was true for all nest types.
We also conducted experiments using domestic chicken eggs to confirm that darker eggshells heated up more rapidly and maintained their incubation temperatures for longer than white eggshells.
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How can penguins and polar bears stay warm in the freezing cold waters of Antarctica? – Riley, age 8, Clarksville, Tennessee USA.
Thanks for your question, Riley. The first thing I should probably say is that while a lot of people think polar bears and penguins live together, in fact they live at opposite ends of the Earth. Polar bears live in the northern hemisphere and penguins live in the southern hemisphere.
I’m a penguin researcher so I’m going to explain here how penguins can stay warm in Antarctica.
There are four species of penguins that live in Antarctica: emperors, gentoos, chinstraps, and Adélies.
All these penguins have special adaptations to keep them warm, but emperor penguins might be the most extreme birds in the world. These amazing animals dive up to 500 metres
below the surface of the ocean to catch their prey, withstanding crushing pressures and water temperatures as low as -1.8℃.
But their most incredible feat takes place not in the ocean, but on the sea ice above it.
Surviving on the ice
Emperor penguin chicks must hatch in spring so they can be ready to go to sea during the warmest time of year. For this timing to work, emperors gather in large groups on sea ice to begin their breeding in April, lay their eggs in May, and then the males protect the eggs for four months throughout the harsh Antarctic winter.
It’s dark, windy, and cold. Air temperatures regularly fall below -30℃, and occasionally drop to -60℃ during blizzards. These temperatures could easily kill a human in minutes. But emperor penguins endure it, to give their chicks the best start in life.
A body ‘too big’ for its head
Emperor penguins have four layers of overlapping feathers that provide excellent protection from wind, and thick layers of fat that trap heat inside the body.
Have you ever noticed that an emperor penguin’s body looks too big for its head and feet? This is another adaptation to keep them warm.
The first place that you feel cold is your hands and feet, because these parts are furthest from your main body and so lose heat easily.
This is the same for penguins, so they have evolved a small beak, small flippers, and small legs and feet, so that less heat can be lost from these areas.
They also have specially arranged veins and arteries in these body parts, which helps recycle their body warmth. For example, in their nasal passages (inside their noses), blood vessels are arranged so they can regain most of the heat that would be lost by breathing.
Male emperor penguins gather close together in big groups called “huddles” to minimise how much of their body surface is exposed to cold air while they are incubating eggs.
This can cut heat loss in half and keep penguins’ core temperature at about 37℃ even while the air outside the huddle is below -30℃.
The biggest huddles ever observed had about 5,000 penguins! Penguins take turns to be on the outer edge of the huddle, protecting those on the inside from the wind.
Incredibly, during this four-month period of egg incubation the male penguins don’t eat anything and must rely on their existing fat stores. This long fast would be impossible unless they worked together.
Emperor penguins are uniquely adapted to their Antarctic home. As temperatures rise and sea ice disappears, emperors will face new challenges. If it becomes too warm they will get heat-stressed, and if the sea ice vanishes they will have nowhere to breed. Sadly, these incredible animals may face extinction in the future. The best thing we can do for emperor penguins is to take action on climate change now.
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Australian summers are getting hotter. Today marks the end of our warmest summer on record, setting new national temperature records. Worsening drought, locally significant flooding, damaging bushfires, and heatwaves capped a summer of extremes.
As we look to autumn, warmer temperatures overall and below average rainfall – especially in eastern parts of the country – are likely.
The starkest feature of this summer was the record warmth. The national average temperature is expected to be about 2.1℃ above average, and will easily beat the previous record high set in summer 2012-13 (which was 1.28℃ warmer than average).
Very low rainfall accompanied the record heat of summer. At the national scale, each month was notably dry, and total summer rainfall was around 30% below average; the lowest for summer since 1982–83. The monsoon onset was delayed in Darwin until the 23rd of January (the latest since 1972–73) and typical monsoonal weather was absent for most of summer.
In December 2018 Australia saw its highest mean, maximum and minimum temperatures on record (monthly averages, compared to all other Decembers). Notable heatwaves affected the north of Australia at the start of the month, spreading to the west and south during the second half of December. Temperatures peaked at 49.3℃ at Marble Bar in Western Australia on the 27th, with mid-to-high 40s extending over larger areas.
The heat continued into January, which set a national monthly mean temperature record at 2.91℃ above the 1961–1990 average. Heatwave conditions which had emerged in December persisted, with a prolonged warm spell and numerous records set. Eight of the ten hottest days for the nation occurred during the month, while a minimum temperature of 36.6℃ at Wanaaring (Borrona Downs) in western New South Wales on the 26th set a new national minimum temperature record.
Temperatures moderated a little in the east of the country for February, partly in response to flooding rainfall in tropical Queensland. Even so, the national mean temperature will come in around 1.4℃ above average, making this February likely to be the fourth or fifth warmest on record.
…and very dry
Australia has seen dry summers before and many of these have been notably hot. The summers of 1972–73 and 1982–83 – which featured mean temperatures 0.90℃ and 0.92℃ above average, respectively – both came during the latter stages of significant droughts, and were both records at the time.
As the State of the Climate 2018 report outlines, Australia has warmed by just over 1℃ since 1910, with most warming occurring since 1950. This warming means global and Australian climate variability sits on top of a higher average temperature, which explains why 2018-19 was warmer again.
A major rain event affected tropical Queensland during late January to early February, associated with a slow-moving monsoonal low. Some sites had a year’s worth of rain in a two-week period, including Townsville Airport which had 1,257mm in ten days. Many Queenslanders affected by this monsoonal low went from drought conditions to floods in a matter of days. Flooding was severe and continues to affect rivers near the Gulf of Carpentaria, as well as some inland rivers which flow towards Kati Thanda–Lake Eyre.
The outlook for autumn
Spring 2018 saw a positive Indian Ocean Dipole which faded in early summer. At the start of summer sea surface temperature anomalies in the central Pacific exceeded 0.8℃, which is the typical threshold for El Niño affecting the oceans, but these declined as summer progressed. Combined with a lack of coupling between the atmosphere and ocean, the El Niño–Southern Oscillation remained neutral, though normal rainfall patterns shifted to oceans to the north and east, leaving Australia drier as a result.
As we move into autumn, the El Niño–Southern Oscillation and Indian Ocean Dipole tend to have less influence at this time of year. The onset of new Indian Ocean Dipole or El Niño/La Niña events typically happens in late autumn or winter/spring.
Over recent years, autumn rainfall has also become less reliable, with declines in cool season rainfall in the southeast and southwest. Temperatures are also rising, in a local expression of the global warming trend.
The Bureau’s outlook for autumn shows high probabilities that day and night-time temperatures will remain above average for most of the country. We expect to see continued below-average rainfall in much of the east, where drought is currently widespread.
Looking to the winter, the Bureau’s ENSO Wrap-Up suggests the Pacific Ocean is likely to remain warmer than average. The potential for an El Niño remains, with approximately a 50% chance of El Niño developing during the southern hemisphere autumn or winter, twice the normal likelihood.
The ocean currents that help warm the Atlantic coasts of Europe and North America have significantly slowed since the 1800s and are at their weakest in 1600 years, according to new research my colleagues and I have conducted. As we’ve set out in a new study in Nature, the weakening of this ocean circulation system may have begun naturally but is probably being continued by climate change related to greenhouse gas emissions.
This circulation is a key player in the Earth’s climate system and a large or abrupt slowdown could have global repercussions. It could cause sea levels on the US east coast to rise, alter European weather patterns or rain patterns more globally, and hurt marine wildlife.
We know that at the end of the last major ice age, rapid fluctuations in the circulation led to extreme climate shifts on a global scale. An exaggerated (but terrifying) example of such a sudden event was portrayed in the 2004 blockbuster film The Day After Tomorrow.
The recent weakening we have found was likely driven by warming in the north Atlantic and the addition of freshwater from increased rainfall and melting ice. It has been predicted many times but, until now, just how much weakening has already occurred has largely remained a mystery. The extent of the changes we have discovered comes as a surprise to many, including myself, and points to significant changes in the future.
The circulation system in question is known as the “Atlantic Meridional Overturning Circulation” (AMOC). The AMOC is like a giant conveyor belt of water. It transports warm, salty water to the north Atlantic where it gets very cold and sinks. Once in the deep ocean the water flows back southwards and then all around the world’s oceans. This conveyor belt is one of the most important transporters of heat in the climate system and includes the Gulf Stream, known for keeping western Europe warm.
Climate models have consistently predicted that the AMOC will slow down due to greenhouse gas warming and associated changes in the water cycle. Because of these predictions – and the possibility of abrupt climate changes – scientists have monitored the AMOC since 2004 with instruments strung out across the Atlantic at key locations. But to really test the model predictions and work out how climate change is affecting the conveyor we have needed much longer records.
Looking for patterns
To create these records, our research group – led by University College London’s Dr David Thornalley – used the idea that a change in the AMOC has a unique pattern of impact on the ocean. When the AMOC gets weaker, the north-eastern Atlantic Ocean cools and parts of the western Atlantic get warmer by a specific amount. We can look for this pattern in past records of ocean temperature to trace what the circulation was like in the past.
Another study in the same issue of Nature, led by researchers at the University of Potsdam in Germany, used historical observations of temperature to check the fingerprint. They found that the AMOC had reduced in strength by around 15% since 1950, pointing to the role of human-made greenhouse gas emissions as the primary cause.
In our paper, which also forms part of the EU ATLAS project, we found the same fingerprint. But instead of using historical observations we used our expertise in past climate research to go back much further in time. We did this by combining known records of the remains of tiny marine creatures found in deep-sea mud. Temperature can be worked out by looking at the amounts of different species and the chemical compositions of their skeletons.
We were also able to directly measure the past deep ocean current speeds by looking at the mud itself. Larger grains of mud imply faster currents, while smaller grains mean the currents were weaker. Both techniques point to a weakening of the AMOC since about 1850, again by about 15% to 20%. Importantly, the modern weakening is very different to anything seen over the last 1,600 years, pointing to a combination of natural and human drivers.
The difference in timing of the start of the AMOC weakening in the two studies will require more scientific attention. Despite this difference, both of the new studies raise important questions regarding whether climate models simulate the historical changes in ocean circulation, and whether we need to revisit some of our future projections.
However, each additional long record makes it easier to evaluate how well the models simulate this key element of the climate system. In fact, evaluating models against these long records may be a crucial step if we hope to accurately predict possible extreme AMOC events and their climate impacts.
For the Arctic, like the globe as a whole, 2016 has been exceptionally warm. For much of the year, Arctic temperatures have been much higher than normal, and sea ice concentrations have been at record low levels.
The Arctic’s seasonal cycle means that the lowest sea ice concentrations occur in September each year. But while September 2012 had less ice than September 2016, this year the ice coverage has not increased as expected as we moved into the northern winter. As a result, since late October, Arctic sea ice extent has been at record low levels for the time of year.
These record low sea ice levels have been associated with exceptionally high temperatures for the Arctic region. November and December (so far) have seen record warm temperatures. At the same time Siberia, and very recently North America, have experienced conditions that are slightly cooler than normal.
We used forecast temperatures and heat persistence models to predict what will happen for the rest of December. But even with 10 days still to go, it is clear that November-December 2016 will certainly be record-breakingly warm for the Arctic.
Next, I investigated whether human-caused climate change has altered the likelihood of extremely warm Arctic temperatures, using state-of-the-art climate models. By comparing climate model simulations that include human influences, such as increased greenhouse gas concentrations, with ones without these human effects, we can estimate the role of climate change in this event.
To put it simply, the record November-December temperatures in the Arctic do not happen in the simulations that leave out human-driven climate factors. In fact, even with human effects included, the models suggest that this Arctic hot spell is a 1-in-200-year event. So this is a freak event even by the standards of today’s world, which humans have warmed by roughly 1℃ on average since pre-industrial times.
But in the future, as we continue to emit greenhouse gases and further warm the planet, events like this won’t be freaks any more. If we do not reduce our greenhouse gas emissions, we estimate that by the late 2040s this event will occur on average once every two years.
Watching the trend
The group at KNMI used observational data (not a straightforward task in an area where very few observations are taken) to examine whether the probability of extreme warmth in the Arctic has changed over the past 100 years. To do this, temperatures slightly further south of the North Pole were incorporated into the analysis (to make up for the lack of data around the North Pole), and these indicated that the current Arctic heat is unprecedented in more than a century.
The observational analysis reached a similar conclusion to the model study: that a century ago this event would be extremely unlikely to occur, and now it is somewhat more likely (the observational analysis puts it at about a 1-in-50-year event).
The Oxford group used the very large ensemble of Weather@Home climate model simulations to compare Arctic heat like 2016 in the world of today with a year like 2016 without human influences. They also found a substantial human influence in this event.
All of our analysis points the finger at human-induced climate change for this event. Without it, Arctic warmth like this is extremely unlikely to occur. And while it’s still an extreme event in today’s climate, in the future it won’t be that unusual, unless we drastically curtail our greenhouse gas emissions.
As we have already seen, the consequences of more frequent extreme warmth in the future could be devastating for the animals and other species that call the Arctic home.
Geert Jan van Oldenborgh, Marc Macias-Fauria, Peter Uhe, Sjoukje Philip, Sarah Kew, David Karoly, Friederike Otto, Myles Allen and Heidi Cullen all contributed to the research on which this article is based.
You can find more details on all the analysis techniques here. Each of the methods used has been peer-reviewed, although as with the Great Barrier Reef bleaching study, we will submit a research manuscript for peer review and publication in 2017.
I ran out of time yesterday to post about my walk up Yacaaba Headland and how I only just avoided being in a storm that was moving in. So today (it’s actually the 27th July 2012 as I type away) I must get two days of posts done, even if I slip this one in back in time, so to speak (as you can with the post time when posting).
So I decided to do the Yacaaba Headland walk just before lunch and had lunch in the carpark, while reading the paper. Nothing too healthy – I tend to eat far too much junk when I’m on holidays. So it was a bacon & egg roll, as well as a couple of potato scallops and some chips (and coke of course) See Picture at Left. It was really brunch and I needed the energy boost to accomplish the walk. Sounds…