Hot Nectar, Warming Weather and Birds Missing the Spring

To do this experiment, you will need:

Three bowls or washing up basins large enough to put your hand in

- Warm water (NOTE - be careful not to make the water too hot!)

- Cold water, with a few ice cubes in it

- Medium temperature water

How to do the experiment:

1 - Fill one bowl with warm water, one with iced water and one with medium water.

2 - Put one hand into the warm water and one in the iced water for one minute.

3 - Take your hands out of the water and put them both into the medium water. How does the water feel?

So what's going on?

When you put your hands into the medium temperature water, the hand that's been in the cold water feels warmer while the one that was in the warm water feels cold.

Why is this?

It's because your senses are relative. They don't measure an absolute temperature or an absolute brightness of light; they make their measurements relative to the things around it. In the case of this experiment, the temperature sensors on your hands measure the temperature of the water relative to the temperature of your hand. If the water is warmer than your hand, it feels warm, and if it is colder than your hand, it feels cold.

Measuring temperature relative to a certain object (such as your hand) is fine if your hand stays at a constant temperature - but it doesn't. If you keep your hand in cold water for a long time, the temperature of your hand starts to drop. This means that the reference point to judge temperature by has changed. Water that once felt cold now feels relatively warm compared to your cold hand.

The opposite happens when you transfer your hand from the hot water into the medium water. Your hand is warm and so the medium water feels relatively cold.

The effect is most obvious in this experiment when you transfer a cold and a hot hand into medium temperature water at the same time: one hand is telling you the water is warm while the other is saying that it's cold, even though the actual temperature of the water is the same throughout!

Your hands give two different answers and your senses are confused!

This effect can be seen in other situations too. When people run a bath they generally tend to stir it with one hand. As a result, people should always test the water with the OTHER hand before getting in. This is because the hand that's been stirring will get used to the high temperature and send messages to the brain saying that the water isn't hot. However, as soon as you jump in with cold feet, the water will feel relatively scalding - so be warned!

Another example is when children are told not to wear their coats indoors because they won't feel the benefit. If you get used to being really hot and snuggly inside a coat in the house, as soon as you go outside you feel cold (like the hot hand going into medium water). However, if you keep your coat on the peg while in the house and only put it on outside, the addition of a warm coat to a warm (rather than hot) body means that the shock of braving a cold winter's day is relatively less.

You can even see this effect with your ears! If you've been in a noisy room and then move into another room that's playing a quiet radio, you can hardly hear it at all. However, if you sit there for five minutes you can start to hear the radio loudly, even though it's still at the same volume.

So the moral of the story is: don't believe everything your senses tell you!

Chris - Here's Beverley Glover from Cambridge University who works on plants and has also found out how they're using jiggery pokery to attract pollinating insects. What's your work about and how is this all achieved?

Beverley - What we're interested in are the adaptations flowers have that make them particularly attractive to pollinators. If you think about a flower, the petals - the bright shiny bit that you like to look at - is really there for only one reason: to attract animals. Different plants have come up with different ways of making those attractive to animals. The one we've been working on most recently is miniature lenses on the petal cells that warm it up a few degrees. We've been doing some work with bumble bees in labs and in flight arenas to test whether they prefer warmer flowers and whether that would be an advantage if the flower could attract more pollinators in the wild.

Chris - And does it work?

Beverley - It seems to work. Having those lens-shaped cells makes the flower warmer and the effect is strongest at dawn and at dusk and we know that bumble bees need extra help at dawn and dusk when it's hard for them to get that big fat body off the ground to fly. So what we've been doing is giving them artificial flowers of different temperatures and seeing whether they prefer the warmer ones and whether they can learn which colours of flowers might be warmer than other colours. It seems as though they can. They can work out that some colours are warmer than others.

Chris - Because the dark colours absorb more energy?

Beverley - Well that would be one way of doing it and it certainly seems that in the wild, from our very early preliminary work, dark coloured flowers are generally warmer than light coloured flowers.

Chris - So why are they all dark then?

Beverley - Because there are all sorts of other ways of doing it and it's not just about warmth. A pollinating animal is interested in being able to spot the flower easily from a distance so it needs visual contrast to the green of the leaves. It also needs to be able to work out where to get into the flower at a short distance, and so there are short distance visual effects. And there's beginning to be some data from work of ours as well about them liking the feel of different flowers, so tactile effects might have a role too. So temperature is just one part of the bag of tricks if you like.

Chris - But why do they like it when it's warmer? Why should that be more attractive?

Beverley - For a bumblebee we think it's about metabolic reward. They need the sugar from the flower to make energy to fly but they, like you on a cold day, might get more energy more quickly from a warm drink than a cold drink. It saves them from using their own energy to warm that nectar up if the flower's already providing it at a warmer temperature.

Helen - And with the bumblebees it's all about being cold blooded. They're not like us mammals; they rely much more on their surroundings to get themselves warm and active for the day's activity.

Beverley - Yes that's right. There's a lot of evidence out there that many insects will back in warm flowers just to get the heat. What we've done that's different is just to show that just warming the flower up by a couple of degrees, just warming the nectar up to give a warmer drink, makes the difference as well. It's not just about sun bathing; it's about getting a warm drink as well.

Chris - How far back in evolutionary terms do you think this goes or is that a very difficult question to answer because there's not a fossil record for plants quite as well as there is for other things?

Beverley - You'd be surprised how good the fossil record for flowers actually is. But it's a difficult question to answer because there's probably a whole range of different ways of warming a flower up and some of them won't fossilise, so for instance tracking the sun. This is not something you'd pick up from a fossil and there are certain plants that do that. The cells we've been looking at, the little lens-shaped ones that warm the flower up, we know that around 80% of flowering plants have those including if not the oldest flowering plant family that's still alive today. Probably the second or third oldest groups have those cells, which suggests that it could have evolved quite early.

Chris - Because insects have been around for quite a few million years. So does that mean that plants have been up to this trick ever since then?

Beverley - It's an interesting question. There's a lot of debate out there as to whether the flowering plants, which are very very rich in species number compared to non-flowering plants, actually underwent that radiation into so many species because the insects were also radiating into so many species at the same time. In the fossil record there are a lot of flowering plants appearing as some of the insect groups expand, so it's possible that that link has been there for quite a long time but it's difficult to prove.

Helen - Well let's stick with changing climate and the changing world around us. As the world warms the permafrost is beginning to melt, which is allowing bacteria to change carbon-rich material laid down over 30 000 years ago into the greenhouse gas methane. But how much gas is being produced? Well it's very difficult to quantify because the bubbles come out of thaw lakes, but Katey Walter from the University of Alaska, Fairbanks has used bubble traps to work out how much methane is emerging. It's enough to increase the methane contribution from the northern wetlands by up to 63%.

Katey - This work is all about quantifying a new source of atmospheric methane which was previously not recognised as a large and significant source, and that is bubbling from thaw lakes, lakes where the permafrost is melting and the lakes continue to expand as they melt into that permafrost, that's where they get the name thaw lakes.

Chris - So how have people tried to measure this in the past, or haven't they?

Katey - In the past scientists have measured methane emissions from lakes in two ways, they measure the diffusive emission where methane moves along a concentration gradient, from the sediments into the atmosphere, and they've done that by just measuring the concentration of methane in the surface water of the lakes. Another source of methane from lakes is bubbling, and that's a much more difficult source of methane to quantify because bubbling is very rare both in space and time.

Chris - So what have you done to get these accurate quantifications of them?

Katey - We have the excellent opportunity in Siberia to study bubbling because when the ice forms on the lakes in Autumn it's like putting a piece of Saran Wrap across the surface of the lakes, it traps the bubbles in place as they wobble to the surface and then they freeze into place in the ice. And we can walk across the ice and map out the distribution of point sources and hot spots.

Chris - So you walk out on the ice, you can see where the bubbles are coming up. But then how do you physically work out how much gas is there?

Katey - We've constructed bubble traps out of greenhouse plastic and copper wire and we place those either under the ice or in the summer when there is no ice we just place them floating under the water surface and each trap captures the bubbles that come up continuously. And so we would go out every day and measure the volume of bubbles that had collected.

Chris - So in the grand scheme of things how much methane is this actually contributing to the global environment?

Katey - Well, scaling up, the type of Siberian lake that we were studying, we estimate that methane emissions from these lakes is about 3.8 teragrams per year. Now, these lakes are only a portion of the northern lakes in general so if bubbling is something that happens everywhere then this could be an even much larger phenomenon than just the scope of our Siberia work. And now we see that just adding this small portion of Siberian lakes to the northern wetland emission estimate it increases it by up to 63%, ten to 63%.

Chris - So what are the implications if you add this to the global warming equation, then?

Katey - This is a new positive feedback to global warming. Methane is a very strong greenhouse gas and so as methane is being produced it is trapped in the atmosphere, increasing atmospheric warming which then enhances the thaw and the expansion of these lakes further. So today there are still about 500 gigatons of carbon remaining in this unique type of Siberian permafrost and it's projected that during the next century the majority of that will degrade and that can release tens of thousands of teragrams more carbon into the atmosphere.

Chris - So should this provoke a rethink of what we think is actually likely to happen in terms of global warming in the future, then?

Katey - Well, one component of the general circulation models that is missing is permafrost degradation, and especially with regards to the large pools of carbon that are stored in permafrost. That carbon content is still poorly known let alone these positive feedbacks to climate change that can happen from permafrost degradation. So yes, we do have a lot of rethinking and incorporation of these new sources.

I have absolutely no idea! They have very sensitive permeable skins so I wonder why they would want you to touch them. Perhaps they have some parasites they want you to scratch off or something!

Not that I know of as their own chloroplasts, but there are more complex multicellular animals out there that pinch the chloroplasts from plants. Quite a few examples are in the cnidarians; that's jellyfish. A little freshwater jellyfish called hydra pinches chloroplasts out of green algae and keeps them in its own gut. It lets them photosynthesise and nicks the sugars that they produce. So there are animals that trick plants out of their chloroplasts.

Well I have to say that it's a term I've not actually heard. But the coldest part of the night is just before the sun comes through. We've lost the daytime moisture and there's still a bit of heat in the ground, but it's just as we go through to the very early hours of the morning that we see the coldest temperatures, so about 5 or 6 o'clock. You can also get a lot of condensation and dew at that time of the morning and that's what can cause lots of these problems as well. So it's a combination of the moisture and the cold temperatures that would have caused the windscreen to freeze out.

That's very true in a certain number of cases. Water in the clouds can exist in liquid form even below temperatures of zero. This is in the form of super-cooled droplets of water. But in the very thick clouds where the cloud top temperatures can be around minus 40 degrees Celsius, most of it does start off as ice. As it falls down, the cloud base is still below zero and it falls as snow and hail. But as it falls through and begins to warm up it does melt down and we actually see it on the surface as rain.

Not a clue! It'll be to do with what the surface is made of, I guess. I don't know the difference: different wax layers maybe?

Galaxies, of course, are not the same as individual stars. The Milky Way galaxy, for example, contains 200 billion stars and is about 150 000 light years across. This means that a star on the opposite side of the Milky Way from our own solar system has been travelling for 150 000 years before it arrives at the Earth. The next nearest galaxy to our own is the Andromeda galaxy and that's about 3 million light years away, so the light that's coming from there is already 3 million years old. So it's beneficial that some suns are very long lived - suns like our sun live for 10 billion years - so there's more than enough time for light to come from the Andromeda galaxy. But you've asked a good question because space is so vast that inevitably light that's coming to us from stars up there in the sky will actually be signs of a star that's died. One day those stars will wink out because they don't exist any more, but at the moment the light is still coming to us because there's a bit of a delay. So there will inevitably be some stars but I doubt there will be a whole galaxy because they contain billions of stars and they'll all be at different phases of their lifetime.