CLIMATE MODELS

Climate models are designed to simulate the responses and interaction of the oceans and atmosphere and to account for changes to the land surface, both natural an human induced.

The models predict that the Earth's average surface temperature will rise. Scientist predict the range of LIKELY temperature increase by running many possible future scenarios. However, these predictions are uncertainly because scientist don't know what choices people will make to control greenhouse gasses emission.

There is a variability between models because not only greenhouse gasses affect but also the effect of aerosols, climate feedbacks (snow and ice, water vapour, clouds and carbon cycle) and ocean cycles like El Niño and La Niña have several influence on temperature changes. 

El Niño and La Niña are opposite phases of what is known as the El Niño-Southern Oscillation (ENSO) cycle.La Niña is sometimes referred to as the cold phase (shrot-term cooling influence on global surface temperatures) and El Niño as the warm phase (we expect temperatures to be above the projection). These desviations from normal surface temperatures can have large-scale impacts not only on ocean processes, but also on global weather and climate.

Further information about El Niño y La Niña cycle:
https://www.climate.gov/enso
http://oceanservice.noaa.gov/facts/ninonina.html
http://www.environmentalscience.org/el-nino-la-nina-impact-environment

Finally, climate models are continously progressing and the simulation of important modes of climate variability has increased the overall confidence in the models’ representation of important climate processes.They can simulate the effect of El Niño and Niña effect, xtreme events, cyclones, cloud feedbacks, cryospheric feedbacks and others.

Further information: 

https://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter8.pdf

Links;

http://www.theguardian.com/environment/climate-consensus-97-per-cent/2014/jul/21/realistic-climate-models-accurately-predicted-global-warming
http://www.theguardian.com/environment/climate-consensus-97-per-cent/2014/jul/21/realistic-climate-models-accurately-predicted-global-warming
http://my2050.decc.gov.uk/?shared=true&user=&percent=17&s=22021222221222

CARBON CYCLE

The carbon cycle is the circulation and transformation of carbon back and forth between living things and the environment. Carbon compounds are present in living things like plants and animals and in nonliving things like rocks and soil.

The amount of carbon on the earth and in Earth's atmosphere is fixed, but that fixed amount of carbon is dynamic, always changing into different carbon compounds and moving between living and nonliving things.

Carbon is released to the atmosphere from what are called "carbon sources" and stored in plants, animals, rocks, and water in what are called "carbon sinks."

There are many carbon sources like these;
Plants.
Through photosynthesis plants take carbon dioxide out of the atmosphere and release oxygen.The carbon dioxide is converted into carbon compounds that make up the body of the plant, which are stored in both the parts of the plants like shoots, leaves and roots.

Animals.
Animals eat the plants, breath in the oxygen, and exhale carbon dioxide. The carbon dioxide created by animals is then available for plants to use in photosynthesis. Carbon stored in plants that are not eaten by animals eventually decomposes after the plants die, and is either released into the atmosphere or stored in the soil.

Geologic processes.
Large quantities of carbon can be released to the atmosphere through geologic processes like volcanic eruptions and other natural changes that destabilize carbon sinks. For example, increasing temperatures can cause carbon dioxide to be released from the ocean.

While a portion of the total amount of carbon present on the earth runs through the carbon cycle relatively quickly, another portion of the carbon is caught up in long-lived and stable carbon sinks.

In Earth’s past, the carbon cycle has changed in response to climate change. Variations in Earth’s orbit alter the amount of energy Earth receives from the Sun and leads to a cycle of ice ages and warm periods like Earth’s current climate. Today, changes in the carbon cycle are happening because of people. We perturb the carbon cycle by burning fossil fuels and clearing land. By burning coal, oil, and natural gas, we accelerate the process, releasing vast amounts of carbon (carbon that took millions of years to accumulate) into the atmosphere every year.

Today we can obtain the data of amount of emissions from the World Bank web site. (http://data.worldbank.org/indicator/EN.ATM.CO2E.PC/countries/CN-GB-US-ES?display=graph)

CO2 emissions (kt)

 

CO2 emissions (metric tons per capita)

These graphics show that China is the the largest producer of CO2 and USA is the greatest producer per capita. However, we can observe that the amount of emissions per capita in some counties have steadily declined since 2007, excepting China.

Since the beginning of the Industrial Revolution, when people first started burning fossil fuels, carbon dioxide concentrations in the atmosphere have risen from about 280 parts per million to 387 parts per million.
 
Nowadays human activity has contributed to an atmospheric concentration of carbon dioxide not seen since the Pliocene epoch between 2.6 and 5.3 million years ago.

Sources:
http://www.esrl.noaa.gov/gmd/ccgg/trends/#mlo_full
http://earthobservatory.nasa.gov/Features/CarbonCycle/

RECENT PAST CLIMATE CHANGE

What are climate change records?

To understand the world's climate and how it was changed, there are many measurements that scientist have to evaluate.

An obstacle in evaluating past climate change is the fact that a lot of observations are not complete. Climate observations were mainly limited to weather situations and ships, and included measurements made near the land or ocean surface. 

In recent years things have improved, ballon soundings have been widespread over the land, satellites have covered all world and there has been an increase in sub-surface monitoring.

But there are no records of measurements bafore 1600s so scientifics have to use other types of information to investigate further back. These kind of data are called indirect or proxy measurements.

They use the tree-rings to determinate the chages in temperature and precipitation. A tree grows and it adds a new ring around its waistline each year so climate conditions have influence in the tree-ring widths.

The ice-cores have accumulated from snowfall over many millennia so, ice cores can tell to scientifics about temperature, precipitation, volcanic activity and wind patterns.

Coral reefs can be used to obtain measurements about temperature and sea-level changes. Corals build their hard skeletons form calcium carbonate. The calcium carbonate contains isotopes of oxygen that can be used to determine the temperature of the water in wich the coras grews.

Finally, scientist can use the polen grains to identify the type of plant from which they came and identify at what time the sediment, where the pollen laid, was deposited.

Sources:  http://www.ncdc.noaa.gov/news/what-are-proxy-data

How volcanos have influence in climate change?

During this week we have seen that the gases and dust particles thrown into the atmosphere during volcanic eruptions have influences on climate.

Volcanic ash or dust released into the atmosphere during an eruption shade sunlight and cause temporary cooling. Larger particles let sunlight in but do not let heat radiation from the Earth’s surface out, and the result is a warmer Earth. Small ash particles form a dark cloud in the troposphere that block some of the incoming energy from the Sun and the Earth cools. Most of these particles fall out of the atmosphere within rain a few hours or days after an eruption. But the smallest particles of dust get into the stratosphere and are able to travel vast distances, often worldwide. These tiny particles are so light that they can stay in the stratosphere for months, blocking sunlight and causing cooling over large areas of the Earth.

Another component has influence in the climate change. Often, erupting volcanoes emit sulfur dioxide into the atmosphere. The sulfur dioxide moves into the stratosphere and combines with water to form sulfuric acid aerosols. The sulfuric acid makes a haze of tiny droplets in the stratosphere that reflects incoming solar radiation, causing cooling of the Earth’s surface. The aerosols can stay in the stratosphere for up to three years, moved around by winds and causing significant cooling worldwide. Eventually, the droplets grow large enough to fall to Earth.

Sources:
http://earthobservatory.nasa.gov/Features/Aerosols/

http://volcano.oregonstate.edu/how-do-volcanoes-affect-atmosphere-and-climate
http://scied.ucar.edu/shortcontent/how-volcanoes-influence-climate


How is today’s warming different from the past?

The Earth’s climate changed due to natural causes in the past. Most often, global climate has changed because of variations in sunlight, the effect of volcanic eruptions, variations in the Earth's orbit and fluctuations in the energy that the sun emits. 

These natural causes have influence today but too small compared to human activity. For example, although volcanoes continue to emit carbon dioxide, the amount of carbon dioxide is extremely small compared to human emission because the world population is a little over a trillion today which implies that carbon dioxide emissions have considerably increased.

Sources: http://earthobservatory.nasa.gov/Features/GlobalWarming/page3.php


What is the role of isotopes in determining temperatures from the past?

The carbonate is the key to know about past temperatures. Originally, carbote is dissolved in the oceans and it forms the shell of a little sea animal, the foraminifera. Studying the shell of this animal through the carbonate that forms it, scientifics can discover how temperatures have changed.

Carbonate contains oxygen, whose atoms exist in two naturally-occurring stable isotopes, ¹⁸O and ¹⁶O.The ratio of these two isotopes in the shells tells us about past temperatures.

The variability of ¹⁸O in the ocean determinates the temperature. This way, when water evaporates in warm climates, the molecules of ¹⁶O tends to evaporate first, so it has more ¹⁸O in places where lots of water evaporates and less where it rains a lot.
¹⁸O isotope is the first to back down into the oceans in form of precipitation, therefore shells have high levels of this isotope.

Changes in climate that alter the global patterns of evaporation or precipitation can therefore cause changes to the background δ¹⁸O ratio.  

Sources: http://www.giss.nasa.gov/research/briefs/schmidt_01/


How have trees been used to reconstruct different climate variables across the world?

Dendrochronology or tree-ring dating is the method of scientific dating based on the analysis of tree ring growth patterns. Tree rings vary in width denpendent on fast or slow growth patterns during warm or cold periods. the density of cells reflects on the growth patterns (low density results in thin rings, high density produces thick rings). Tree could also have diseases or additional enrichment, which result in the varying growth patterns also.

Tree-rings can provide continuous yearly paleoclimatic records for regions or periods of time with no instrumental climate data. However, different species respond to different climate parameters. Scientifics have to consider when dating trees that most trees are not old enough, so the records do not date back as far as other sources of climate data. This is when crossdating is important to identify similar growth patterns across many trees and make a longer timeline of climate data.This way, increasing the amount of trees utilised to study, the best crossdating results can be obtained.

Sources:
http://web.utk.edu/~grissino/principles.htm#1
http://www.windows2universe.org/earth/climate/CDcourses_treerings.html
https://www.ncdc.noaa.gov/news/picture-climate-how-can-we-learn-tree-rings

How can ice cores provide a record of atmospheric composition?

The most important property of ice cores is that they are a direct archive of past atmospheric gasses. Air is trapped at the base of the firn layer, and when the compacted snow turns to ice, the air is trapped in bubbles.The air bubbles are extracted by melting, crushing or grating the ice in a vacuum.This method provides detailed records of carbon dioxide, methane and nitrous oxide going back over 650,000 years

Also, it is possible to discern past air temperatures from ice cores. This can be related directly to concentrations of carbon dioxide, methane and other greenhouse gasses preserved in the ice. The ratio of oxygen isotopes in the snow reveals temperature, though in this case, the ratio tells how cold the air was at the time the snow fell. In snow, colder temperatures result in higher concentrations of light oxygen.

Sources:
http://www.antarcticglaciers.org/glaciers-and-climate/ice-cores/ice-core-basics/
http://www.earthobservatory.nasa.gov/Features/Paleoclimatology_IceCores/

PAST CLIMATE CHANGE

When we think about climate change it's easy to wonder what happened in the past. This week we are going to learn more about how our climate has changed over the last 4.5 billion years.

The Earth's climate has changed many times before. There have been times when most of the planet was covered in ice, and there have also been much warmer periods. Over at least the last years, temperatures and carbon dioxide levels in the atmosphere have increased and decreased in a cyclical pattern.

To understand this cyclical pattern the BBC has published a series of documentaries on snowball Earth. Link or Youtube

Snowball Earth describes the coldest climate inmaginable. In the distant past the Earth froze over from pole to pole. 

But, how could it be possible?

We know that our climate is controlled by some feedbacks and cycles, particulary in this case, the ice albedo feedback, the water cycle and the carbon dioxide cycle. 

 

ICE ALBEDO FEEDBACK

These cycles can be summarised in this diagram which explain the process of the snowball Earth theory:

 

Amazingly, the Earth is capable of selfregulating, with a series of mechanisms that work together and surprisingly gases like carbon dioxide played a powerful role in governing global climate.

Further information in these links;
Snowball Earth
http://www.bbc.co.uk/nature/ancient_earth/Snowball_Earth
https://www.youtube.com/watch?v=Dv0e-zGGgjQ 
http://globalwarmingsimplified.weebly.com/ 

THE CLIMATE SYSTEM, FEEDBACKS, CYCLES AND SELF-REGULATION

Our climate is a system that it is controlled by positive and negative feedbacks as well as natural cycles.

As a system, we can distinguish 5 key components ( the atmosphere, hydrosphere, biosphere, cryosphere and lithosphere ). These components intetract between them through a series of cycles that link every component to another.

 

There are a lot of natural cycles, but a good example is the water cycle.In the picture below you can observe how it works.

To determine the climate state of the Earth is needed to undesrtand the feedbacks that operate in the climate system. There are 3 key feedbacks, water vapour feedback, ice albedo feedback and the radiation feedback.

The water vapor feedback is a positive feedback (in a mathematical way) and has three components: temperature, evaporation and water vapour. If we incresase the temperature, the evaporation increases.

The ice albedo feedback has a significant influence on the climate. The ice reflects so much solar radiation back to the atmosphere because it has a high albedo. On the other hand, the ocean tends to absorb more that it reflects because it has a low albedo, for this reason the ocean is heating. This means that the warming of the ocean will melt the sea ice.

The last feedback is the radiation feedback, it is a good example of negative feedback. It works by cooling an object when the temperature is rising. All objects give off radiation, but the warmer a body is the more radiation it gives off.

To sump up, climate can be conceived as a system that involves different components. The mixture of positive and negative feedbacks cooperates to a self-regulation of the climate system.

DIFFERENCE BETWEEN WEATHER AND CLIMATE

According to the NASA web;

The difference between weather and climate is a measure of time. Weather is what conditions of the atmosphere are over a short period of time, and climate is how the atmosphere "behaves" over relatively long periods of time.

In most places, weather can change from minute-to-minute, hour-to-hour, day-to-day, and season-to-season. Climate, however, is the average of weather over time and space. An easy way to remember the difference is that climate is what you expect, like a very hot summer, and weather is what you get, like a hot day with pop-up thunderstorms.

In Ourense where I live the climate is Oceanic type which is generally characterized by mild temperatures all year round, with maximun in summer and minimun in winter, and also rainfall throughout the year, with a maximun in winter and a minimun in summer.