
The ocean is taking up twice as much heat now as it was just two decades ago, relative to pre-industrial times. According to new research, a third of that heat—and rising—is finding its way into the deep ocean below 700m, temporarily slowing warming at Earth’s surface.
That the oceans are warming isn’t a surprise to scientists—it’s what we would expect from rising greenhouse gases. The more surprising part is the speed at which it is taking place.
The new study, published yesterday in Nature Climate Change, says as much heat entered the oceans in the last 18 years as in the previous 130 years.
The new findings add to a growing body of research on the unseen impact of human activity on the oceans and the role they play in moderating the temperature we feel on Earth’s surface, say scientists not involved in the study.
A Brief History
The oceans take up more than 90 percent of the heat trapped by greenhouse gases. It follows, then, that we would look to the oceans in seeking the fingerprint of human-caused climate change.
Scientists have been studying the oceans for hundreds of years. The Challenger expedition in the 1870s was considered the first real oceanographic voyage, bringing back with it reams of data from previously unexplored parts of the world, from the ocean surface to the sea floor.
Scientists’ instruments have changed a lot over time, from lowering buckets over the sides of wooden ships to the global fleet of drifting floats we have today, known as the ARGO array. Separating real changes in ocean heating from artefacts of switching from old to new methods is one of the biggest challenges in understanding how the oceans have changed over time.
Model Match
The new study begins by compiling several different sets of observational measurements, from the Challenger expedition right up to the present day.
These include ship-based surveys of the upper ocean down to 700m repeated every year since the 1960s, temperature data down to 2,000m collected by ARGO floats since 2005 and transects carried out by ships extending down to below 2,000m in some parts of the world.
The observational data are far from perfect. There are many areas with sparse data, which means reliably estimating changes to ocean heat content is difficult using observations alone.
To address this, the study compares the different observational datasets with simulations from climate models (CMIP5) used in the latest Intergovernmental Panel on Climate Change, forced with historically realistic levels of greenhouse gases, emissions from land use, changes in solar activity and the temporary cooling effect of volcanic eruptions.
On the whole, the observations compared well with the average from the model simulations at all depths considered (0-700m, 700-2000m and below 2,000m). And it was passing this reliability test that allowed the scientists to cast the models backwards and examine how heat content in the oceans today compares to pre-industrial times.
Double Trouble
For the ocean as a whole, the authors find that 50 percent of the heat taken up since 1865 has occurred since 1997. In other words, the oceans have absorbed as much heat in the past 18 years as in the previous 130 years, the paper notes.
The study also find that while most of the heat stayed in the upper ocean, about 35 percent found its way to the deep ocean below 700m—and that fraction has increased steadily over time.
These new findings largely confirm what scientists already knew about human-induced climate change, says Dr. Matt Palmer from the Met Office Hadley Center:
"This research shows the strengthening of the climate change signal over time and that more of this signal is finding its way into the deep ocean."
The study also confirms that while temperatures at Earth’s surface have risen more slowly over the past 10-15 years than in previous decades—a familiar feature if you look back at Earth’s full temperature record—there has been no such change of pace in the oceans. Palmer adds:
"[The study] confirms that ocean heat uptake has been proceeding at the expected rate—the ‘hiatus’ is a surface phenomenon. The Earth is still warming and the oceans have been taking up the bulk of that heat."
The novel part of today’s study comes in the comparison of observations with climate models—particularly below 700m—and the comparison of ocean heat content now with preindustrial times. Scientists’ interest in studying the deep ocean has been driven partly by a wish to understand the behaviour of surface temperatures in recent times but mostly by advances in the ways available to monitor ocean temperature, says Palmer.
Bigger Picture
There is still some work to do in pinning down exactly how much heat the oceans have taken up in the past two decades and whether that can account for the whole so-called slowdown in surface warming, the paper notes. That’s not as straightforward as it sounds, largely because of how to account for the transition to ARGO floats from traditional methods, the paper notes.
Another point to note is that the climate models used do not include volcanic eruptions after 2000, which the authors estimate could offset the rise in global temperature by around 7 percent.
While the oceans seem to have slowed warming at the Earth’s surface in recent decades, this shouldn’t be interpreted as a good thing, says Prof. John Shepherd from the National Oceanography Center in Southampton. He says:
"Once the ocean heat uptake settles down again, the rate of warming is likely to return to what it was before."
How the ocean acts to moderate surface temperatures is vital for understanding how our planet responds to greenhouse gases over the long term, a concept known as the “climate sensitivity." The mechanisms and timescales at play are critical pieces of that ongoing puzzle.
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By Daisy Simmons
In a wildfire, hurricane, or other disaster, people with pets should heed the Humane Society's advice: If it isn't safe for you, it isn't safe for your animals either.
1. Stay Informed
<p>A first order of business in pet evacuation planning is to understand and be ready for the possible threats in your area. Visit <a href="https://www.ready.gov/be-informed" target="_blank">Ready.gov</a> to learn more about preparing for potential disasters such as floods, hurricanes, and wildfires. Then pay attention to related updates by tuning <a href="http://www.weather.gov/nwr/" target="_blank">NOAA Weather Radio</a> to your local emergency station or using the <a href="https://www.fema.gov/mobile-app" target="_blank">FEMA app</a> to get National Weather Service alerts.</p>2. Ensure Your Pet is Easily Identifiable
<p><span>Household pets, including indoor cats, should wear collars with ID tags that have your mobile phone number. </span><a href="https://www.avma.org/microchipping-animals-faq" target="_blank" rel="noopener noreferrer">Microchipping</a><span> your pets will also improve your chances of reunion should you become separated. Be sure to add an emergency contact for friends or relatives outside your immediate area.</span></p><p>Additionally, use <a href="https://secure.aspca.org/take-action/order-your-pet-safety-pack" target="_blank" rel="noopener noreferrer">'animals inside' door/window stickers</a> to show rescue workers how many pets live there. (If you evacuate with your pets, quickly write "Evacuated" on the sticker so first responders don't waste time searching for them.)</p>3. Make a Pet Evacuation Plan
<p> "No family disaster plan is complete without including your pets and all of your animals," says veterinarian Heather Case in <a href="https://www.youtube.com/watch?v=Q9NRJkFKAm4" target="_blank">a video</a> produced by the American Veterinary Medical Association.</p><p>It's important to determine where to take your pet in the event of an emergency.</p><p>Red Cross shelters and many other emergency shelters allow only service animals. Ask your vet, local animal shelters, and emergency management officials for information on local and regional animal sheltering options.</p><p>For those with access to the rare shelter that allows pets, CDC offers <a href="https://www.cdc.gov/healthypets/emergencies/pets-in-evacuation-centers.html" target="_blank">tips on what to expect</a> there, including potential health risks and hygiene best practices.</p><p>Beyond that, talk with family or friends outside the evacuation area about potentially hosting you and/or your pet if you're comfortable doing so. Search for pet-friendly hotel or boarding options along key evacuation routes.</p><p>If you have exotic pets or a mix of large and small animals, you may need to identify multiple locations to shelter them.</p><p>For other household pets like hamsters, snakes, and fish, the SPCA recommends that if they normally live in a cage, they should be transported in that cage. If the enclosure is too big to transport, however, transfer them to a smaller container temporarily. (More on that <a href="https://www.spcai.org/take-action/emergency-preparedness/evacuation-how-to-be-pet-prepared" target="_blank" rel="noopener noreferrer">here</a>.)</p><p>For any pet, a key step is to establish who in your household will be the point person for gathering up pets and bringing their supplies. Keep in mind that you may not be home when disaster strikes, so come up with a Plan B. For example, you might form a buddy system with neighbors with pets, or coordinate with a trusted pet sitter.</p>4. Prepare a Pet Evacuation Kit
<p>Like the emergency preparedness kit you'd prepare for humans, assemble basic survival items for your pets in a sturdy, easy-to-grab container. Items should include:</p><ul><li>Water, food, and medicine to last a week or two;</li><li>Water, food bowls, and a can opener if packing wet food;</li><li>Litter supplies for cats (a shoebox lined with a plastic bag and litter may work);</li><li>Leashes, harnesses, or vehicle restraints if applicable;</li><li>A <a href="https://www.avma.org/resources/pet-owners/emergencycare/pet-first-aid-supplies-checklist" target="_blank">pet first aid kit</a>;</li><li>A sturdy carrier or crate for each cat or dog. In addition to easing transport, these may serve as your pet's most familiar or safe space in an unfamiliar environment;</li><li>A favorite toy and/or blanket;</li><li>If your pet is prone to anxiety or stress, the American Kennel Club suggests adding <a href="https://www.akc.org/expert-advice/home-living/create-emergency-evacuation-plan-dog/" target="_blank" rel="noopener noreferrer">stress-relieving items</a> like an anxiety vest or calming sprays.</li></ul><p>In the not-unlikely event that you and your pet have to shelter in different places, your kit should also include:</p><ul><li>Detailed information including contact information for you, your vet, and other emergency contacts;</li><li>A list with phone numbers and addresses of potential destinations, including pet-friendly hotels and emergency boarding facilities near your planned evacuation routes, plus friends or relatives in other areas who might be willing to host you or your pet;</li><li>Medical information including vaccine records and a current rabies vaccination tag;</li><li>Feeding notes including portions and sizes in case you need to leave your pet in someone else's care;</li><li>A photo of you and your pet for identification purposes.</li></ul>5. Be Ready to Evacuate at Any Time
<p>It's always wise to be prepared, but stay especially vigilant in high-risk periods during fire or hurricane season. Practice evacuating at different times of day. Make sure your grab-and-go kit is up to date and in a convenient location, and keep leashes and carriers by the exit door. You might even stow a thick pillowcase under your bed for middle-of-the-night, dash-out emergencies when you don't have time to coax an anxious pet into a carrier. If forecasters warn of potential wildfire, a hurricane, or other dangerous conditions, bring outdoor pets inside so you can keep a close eye on them.</p><p>As with any emergency, the key is to be prepared. As the American Kennel Club points out, "If you panic, it will agitate your dog. Therefore, <a href="https://www.akc.org/expert-advice/home-living/create-emergency-evacuation-plan-dog/" target="_blank" rel="noopener noreferrer">pet disaster preparedness</a> will not only reduce your anxiety but will help reduce your pet's anxiety too."</p>Evacuating Horses and Other Farm Animals
<p>The same basic principles apply for evacuating horses and most other livestock. Provide each with some form of identification. Ensure that adequate food, water, and medicine are available. And develop a clear plan on where to go and how to get there.</p><p>Sheltering and transporting farm animals requires careful coordination, from identifying potential shelter space at fairgrounds, racetracks, or pastures, to ensuring enough space is available in vehicles and trailers – not to mention handlers and drivers on hand to support the effort.</p><p>For most farm animals, the Red Cross advises that you consider precautionary evacuation when a threat seems imminent but evacuation orders haven't yet been announced. The American Veterinary Medical Association has <a href="https://www.avma.org/resources/pet-owners/emergencycare/large-animals-and-livestock-disasters" target="_blank">more information</a>.</p>Bottom Line: If You Need to Evacuate, So Do Your Pets
<p>As the Humane Society warns, pets left behind in a disaster can easily be injured, lost, or killed. Plan ahead to make sure you can safely evacuate your entire household – furry members included.</p>- 5 Ways to Be an Eco-Friendly Pet Owner - EcoWatch ›
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