Welcome to the sixth of our weekly areas of focus on climate action, providing encouragement and seeking to inspire action within all the 22 Methodist Churches in the Ipswich area.
By the time the COP26 summit begins on 1st November, we will have covered 9 distinct areas of concern.
This week’s focus
This week we are looking at Changing Airstreams and Currents.
Much of the sun’s energy is absorbed in the tropical oceans, before it is distributed around the world along ocean currents acting as transport highways for heat. Airstreams high in the atmosphere provide a second important, but much less efficient mechanism to transfer energy round the world.
These Airstreams and Ocean Currents are vulnerable to climate change, whilst also being agents in driving its impact.
Why are Ocean Currents and Airstreams Important for the Climate?
A disproportionate amount of the sun’s energy reaching earth is absorbed in the equatorial and tropic ocean regions. This energy is then spread around the world by major ocean currents flowing out towards the poles, using the Atlantic and Pacific oceans as vast energy highways.
Air currents provide an alternative mechanism for transferring heat from hot to cold regions. As air is warmed in the tropics, it becomes less dense, rising high into the atmosphere, flowing towards the colder regions, becoming denser as it cools. These air currents flow high in the atmosphere and unlike the ocean currents, air streams traverse both land and sea. The path of the air currents is strongly influenced by the underlying geography – both its topology and its surface characteristics. Glider pilots rely heavily on their understanding of these air currents, seeking out thermals that can prolong their flights.
Water has a high capacity to carry heat, so the ocean streams are particularly effective at taking heat away from the tropics to higher latitudes. Airstreams high in the atmosphere carry smaller amounts of energy, but have more freedom to redistribute energy over both land and sea. Both play a major role in long term climate and individual weather events.
It is difficult to comprehend how important these currents are in our everyday lives. We take them for granted with little need to understand them and no means to influence them on a day-to-day basis. What if they didn’t exist?
Without these ocean currents acting as huge conveyor belts transferring heat away from the tropical zones out towards the cold polar regions, life on earth would be impossible. The tropics would be unbearably hot without any mechanism for cooling. The land would be baked and barren, with water evaporating long before it could create rivers or lakes. Devoid of warming energy, the poles would face ultra-low freezing conditions, with ice permanently covering larger expanse than today.
Copyright David Welbourn
In the absence of ocean currents, the airstreams high in the atmosphere would take on the sole role of redistributing energy around the world. Air currents are much less effective at transporting energy then water currents, but faced with the higher temperature gradient between equator and pole, these air currents would flow much faster to compensate, creating more violent, turbulent stormy conditions on a near-permanent basis.
These energy highways play a major role in dictating prevailing climate and localised weather events.
More about Ocean Currents
The schematic image above illustrates how the Great Ocean Conveyor moves vast quantities of water on thermal gradients around the globe transferring the energy away from the tropical regions to the poles, using the major oceans as the highways. The Atlantic and Pacific oceans provide pathways to the North Pole, and together with the Indian Ocean they provide highways to the Southern Ocean where all the currents combine.
In the UK, we are probably familiar with the Gulf Stream flowing from the Caribbean, past the tip of Florida and leading all the way up the coast of Norway to the Arctic Circle, with side branches speading round Iceland, Greenland and the New England Coast. This flow creates temperate conditions which are far warmer throughout the year than latitude alone would predict.
Japan too benefits from a similar flow known as the Kuroshio Current, carrying warm waters from the South China Sea up towards the Bering Sea.
Each of these warm surface currents has a cold stream carrying colder water deeper in the ocean. These flows provide much more than temperate climate to the lands they touch. The surface temperature of the ocean affects the ground-level air currents. Changes in water density and mineral/ nutrient solubility also provide distinct boundaries for marine life, defining rich fishing zones.
In 2009-2010, there was a sudden warming of the Northwest Atlantic Shelf off the US Eastern seaboard, which had significant economic consequences to the fisheries. This was eventually shown to have been caused by a shift in the path of the Gulf Stream in 2008 which prevented cold (nutrient rich) water flowing south from Labrador leading to a permanent shift in that area of coastal ecosystem.
Research published in Nature early in 2021 shows that the flow of the Guulf Stream is continuing to slow as a direct result of human activity driving climate change. The flow is predicted to continue slowing and changing course, likely to reach a tipping point when the flow will become unstable with irreversible consequences. A radical change to the path of the gulfstream will have major consequences to countries bordering the Atlantic, with colder average conditions and even more frequent extremes. The prevailing north-easterly direction of the flow depresses sea-levels on the Arlantic coast of USA. Loss of the Gulf Stream will have a major impact on weather conditions on both sides of the Atlantic, but will also amplify the rise in sea-levels along the US coast.
More about Airstreams
Between 6 and 10 miles above the earth’s surface, major fast flowing currents of air circle the earth. These currents of air, called jetstreams, are hundreds of miles wide and can flow over 200 mph as they circle around the earth. There is a polar front jet and a subtropical jet in each of the northern and southern hemisphere. Each jet marks a boundary between cold and warm air. The sharp temperature difference creates a pressure gradient creating the high speed winds of the jetstream. The exact location and pattern of flow of these jetstreams varies with time and season and is affected by the surface temperature over which the air flows. The UK lies close to the path of the polar front jetstream – bringing cold air from the arctic when the flow is southerly down the eastern side of the Atlantic, swinging eastwards over southern europe. Conversely, it draws warm air from subtropical regions when the flow is to the north of the UK. Weather forecasters frequently use maps showing changes to the jetstream flow to explain predicted changes in weather conditions, especially when the path of the jetstream is crossing directly over the country.
Typical paths for the polar and subtropical jetstreams in the northern hemisphere are shown on the attached schematic.
The Met Office has published a video for anyone seeking to understand the physics of jetstreams and why they have such a big influence on UK weather.
The jetstreams circulate from west to east, counter to the rotation of the earth, with fluctuations north or south appearing like waves in the flow. these are influenced by other conditions, particularly the temperature and charectristics of the surface structure and topology
licensed by Comet Terms, University Corporation for Atmospheric research
Other airstreams transport water vapour from the hot tropical regions where seawater evaporates, eventually causing precipitation where temperature or pressure conditions cause a sudden change to the airflow. This dense humid air flow carries volumes of water similar to that carried by major rivers cascading from mountain sources to the seas and oceans. These atmospheric rivers frequently deposit their payload of water as snow or rain as they hit landfall.
Occasionally, the jet stream and these atmospheric rivers “collide”, causing persistent weather conditions. The jetstream path becaomes stationary whilst the vapour-filled atmospheric river continues delivering more moisture pouring contiuously over the same area, causing serious flooding. This blocking process is predicted to become more frequent under climate change, with more vapour being delivered and greater likelihood that the high pressures air masses remain stationary for prolonged periods.
Clouds
If the ocean currents and the airstreams are the highways transporting energy out of the hot tropical regions to spread the heat to higher latitudes, then clouds are the other piece of the jigsaw bridging between the two.
Rising global temperatures will cause more moisture to evaporate from open water surfaces, whether oceans, seas, lakes or rivers. The airstreams and atmospheric rivers move this high density air towards the colder regions, with the moisture eventually falling as precipitation.
Overcast grey skies form when high vapour content creates high density, low level stratus clouds remaining close to the earth. These will tend to block the sun’s rays, reducing their warming effect. These clouds will have a net cooling effect.
In contrast, clouds with low vapour content have hot, low density air that will rise high above the earth. These wispy cirrus clouds will allow sunlight to pass through, which they will then trap, increasing the global warming effect.
Other types of cloud will combine the effects of partially blocking and partially trapping the energy in the sun’s rays, with variable effect on the degree of warming.
Changes in the ocean streams, the jetstreams and the types of cloud forming will all interact as the overall temperature of the planet continues to rise, creating feedback loops in which the faster the planet warms, the more the warming mechanisms win-out over those which have a cooling effect, and vice-versa. Some extreme models of geo-engineering suggest that we could engineer changes increasing the cooling effects (e.g. scattering reflective particles into very high altitude clouds to reflect more sunlight away from earth).
What Can we Do?
Across all nine of our focus areas in this climate justice campaign, this topic of Changes to Airstreams and Ocean Currents is the one area over which we have least direct influence. The forces of nature involved are beyond the reach of individuals, and the changes can only be halted by concerted action to slow down and reverse the global warming effects, before it is too late to prevent the ocean currents and airstreams failing or changing course irrevocably.
More than any other area, this is the one in which the power of infomed lobbying is especially important, together with the power of informed prayer. Changes to airstreams and currents occur slowly, but inexorably. Most experts predict that there is a tipping point of no return, somewhere ahead. As a topic, it is the easiest but most dangerous one to kick into the long grass through inaction.
Given the apparent anomaly, that global warming may lead to colder conditions in the UK, will that reinvigrate climate deniers, claiming that warming must be fake news? Campaigners for climate justice must be ready to counter such ill-informed messages.
It is important to make sure your voice is heard. Speak out and support campaigns which:
- demand more rapid implementation of energ reduction schemes;
- accelerate the enforcement of new building regulations to ensure every new home is built to net zero or better standards;
- press government to introduce taxation policies to penalise climate damaging actions whilst rewarding climate sensitive action;
- encourage new advertising standards banning greed-fuelled promotions;
- hold business leaders to account for accelerating meaningful environmental policies;
- use the power of your pension fund to back out of fossil fuels
- use your purchasing power in shops to reduce food miles, eliminate waste packaging
Share good news stories of how you’ve made your influence felt.
Learn More
- Learn about ocean currents from the National Oceanic and Atmospheric Administration
- learn more about the Gulf Stream from the Met Office
- learn about the weakening of the Gulf Stream, from University College London
- review of the impact on UK if the Gulf Stream collapses from National World
- what the Guardian environmental correspondent has to say about the Gulf Stream
- learn about Kuroshio Current from the American Geophysical Union
- read about atmospheric rivers from the National Oceanic and Atmospheric Administration
- read about jetstreams from University corporation for AtmophericRresearch
- learn about the Jet Stream from the Met Office or watch their video
- read about Jet Stream, climate change and “blocking” weather events from CarbonBrief
- learn about clouds, precipitation and climate change from the National Centre for Atmospheric Research
- an explanation of the impact of clouds on climate change from Lab Manager
- a tutorial on how clouds affect the climate, from NASA
- why it is important for climate models to understand how clouds affect the climate, from the Conversation
- see what Greenpeace has to say on the subject
World Environment Day Exemplar
On 5th June 1974, the first World Environment Day was marked. Every year since then, a host city has brought focus to an environmental topic that was particularly pertinent to them.
In 2007, the International Council for Science, had joined forces with the International Meteorological Organisation to designate the year as International Polar Year (IPY) so that they could draw attention to the environmental issues affecting the polar regions. The UN chose Tromsø as their host city for World Environment Day to align themselves with the IPY, so that the voice of all three agencies could shine the light on important findings from the environmental research programmes being conducted in these highly vulnerable regions.
Tromsø slected the theme Melting Ice – a Hot Topic as their focus for the World Environment Day programme. You can read more about this theme by following this link.
This Week’s Prayer
Pray for an understanding of the delicate balance of nature, and its vulnerability to our carelessness, so that we may continue to rejoice in the wonder of God’s creation.
Key Messages
- local climatic conditions are strongly influenced by high altitude jet-streams and long-range sea currents – warmer ocean and land temperatures will seriously disrupt current flow patterns, with substantial regional disparity in severity of climate change;
- temperate regions are likely to experience wide fluctuation and more catastrophic extreme events;
- the impact of clouds on climate change is complex and still not fully understood – some clouds will help to reduce the impact of climate change, whilst others will increase the impact;
- changes in this area are likely to be slow, with occasional step change, but will be easily overlooked as they creep up: utlimately, the changes will be severe and most likely irreversible;
- redoubling informed campaigning urging decision makers to take timely actions that encourage ane reward positive behaviours, whilst penalising anyone who seeks to play a wait and see game.