Which of the following best explains the reasons for the similarities and differences between the two land survey system shown?

Inhaltsverzeichnis Show

What exactly is weather?
What exactly is climate?
Are regional climates different from the global climate?
How does the climate change?
Why do we study climate?

Take a moment and think about the weather today where you are. Is it normal or typical? Is it what you’d expect? If it’s been cool the past few days but the temperature is climbing today, is that weather or climate? Are weather and climate the same thing? Though they are closely related, weather and climate aren’t the same thing. Climate is what you expect. Weather is what actually happens.

What exactly is weather?

More specifically, weather is the mix of events that happen each day in our atmosphere. Even though there’s only one atmosphere on Earth, the weather isn’t the same all around the world. Weather is different in different parts of the world and changes over minutes, hours, days, and weeks.

Most weather happens in the part of Earth’s atmosphere that is closest to the ground—called the troposphere. And, there are many different factors that can change the atmosphere in a certain area like air pressure, temperature, humidity, wind speed and direction, and lots of other things. Together, they determine what the weather is like at a given time and location.

What exactly is climate?

Whereas weather refers to short-term changes in the atmosphere, climate describes what the weather is like over a long period of time in a specific area. Different regions can have different climates. To describe the climate of a place, we might say what the temperatures are like during different seasons, how windy it usually is, or how much rain or snow typically falls.

When scientists talk about climate, they're often looking at averages of precipitation, temperature, humidity, sunshine, wind, and other measures of weather that occur over a long period in a particular place. In some instances, they might look at these averages over 30 years. And, we refer to these three-decade averages of weather observations as Climate Normals.

Looking at Climate Normals can help us describe whether the summers are hot and humid and whether the winters are cold and snowy at a particular place. They can also tell us when we might expect the warmest day of the year or the coldest day of the year at that location. But, while descriptions of an area’s climate provide a sense of what to expect, they don't provide any specific details about what the weather will be on any given day.

Here’s one way to visualize it. Weather tells you what to wear each day. Climate tells you what types of clothes to have in your closet.

Across the globe, observers and automated stations measure weather conditions at thousands of locations every day of the year. Some observations are made hourly, others just once a day. Over time, these weather observations allow us to quantify long-term average conditions, which provide insight into an area’s climate.

In many locations around the United States, systematic weather records have been kept for over 140 years. With these long-term records, we can detect patterns and trends. And, as the Nation’s official archive for environmental data, it’s our job to collect, quality control, and organize these data and make them available online for scientists, decision makers, and you.

Are regional climates different from the global climate?

Like the United States, different regions of the world have varying climates. But, we can also describe the climate of an entire planet—referred to as the global climate. Global climate is a description of the climate of a planet as a whole, with all the regional differences averaged. Overall, global climate depends on the amount of energy received by the sun and the amount of energy that is trapped in the system. And, these amounts are different for different planets. Scientists who study Earth’s climate look at the factors that affect our planet as a whole.

How does the climate change?

While the weather can change in just a few minutes or hours, climate changes over longer time frames. Climate events, like El Niño, happen over several years, with larger fluctuations happening over decades. And, even larger climate changes happen over hundreds and thousands of years.

Today, climates are changing. Our Earth is warming more quickly than it has in the past according to the research of scientists. Hot summer days may be quite typical of climates in many regions of the world, but warming is causing Earth's average global temperature to increase. The amount of solar radiation, the chemistry of the atmosphere, clouds, and the biosphere all affect Earth's climate.

As global climate changes, weather patterns are changing as well. While it’s impossible to say whether a particular day’s weather was affected by climate change, it is possible to predict how patterns might change. For example, scientists predict more extreme weather events as Earth’s climate warms.

Why do we study climate?

Climate, climate change, and their impacts on weather events affect people all around the world. Rising global temperatures are expected to further raise sea levels and change precipitation patterns and other local climate conditions. Changing regional climates could alter forests, crop yields, and water supplies. They could also affect human health, animals, and many types of ecosystems. Deserts may expand into existing rangelands, and features of some of our National Parks and National Forests may be permanently altered.

Several of our scientists and staff are attending the American Meteorological Society’s (AMS) 23rd Conference on Applied

The online summer meeting of Earth Science Information Partners (ESIP) brings our staff to the virtual table to discuss

Scientists in a range of Earth science fields convene this week to cultivate potential uses of scientific data by end users

Hundreds of scientists will gather in Honolulu, Hawaii, September 16-20, 2019, at a decadal meeting to work toward designing a

Poore, J., & Nemecek, T. (2018). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392), 987-992.
FAO. (2011). The state of the world’s land and water resources for food and agriculture (SOLAW) – Managing systems at risk. Food and Agriculture Organization of the United Nations, Rome and Earthscan, London.
Poore, J., & Nemecek, T. (2018). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392), 987-992.
Bar-On, Y. M., Phillips, R., & Milo, R. (2018). The biomass distribution on Earth. Proceedings of the National Academy of Sciences, 115(25), 6506-6511.
‘Barren land’ refers to land cover in which less than one-third of the area has vegetation or other cover; barren land typically has thin soil, sand or rocks and includes deserts, dry salt flats, beaches, sand dunes, and exposed rocks.
This data is sourced from the UN Food and Agriculture Organization. Other studies confirm this distribution of global land: in an analysis of how humans have transformed global land use in recent centuries, Ellis et al. (2010) found that by 2000, 55% of Earth’s ice-free (not simply habitable) land had been converted into cropland, pasture, and urban areas. This left only 45% as ‘natural’ or ‘semi-natural’ land.

Ellis, E. C., Klein Goldewijk, K., Siebert, S., Lightman, D., & Ramankutty, N. (2010). Anthropogenic transformation of the biomes, 1700 to 2000. Global Ecology and Biogeography, 19(5), 589-606.

The major uncertainties – and explanation for discrepancies – in these assessments is the allocation of ‘rangelands’: in some regions it can be difficult to accurately quantify how much of rangelands are used for grazing, and how much is free from human pressure. Despite this uncertainty, most analyses tend to converge on an estimate of close to half of habitable land being used for agriculture.
Poore, J., & Nemecek, T. (2018). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392), 987-992.

The UN Food and Agriculture Organization (FAO) provide global statistics on crop and food production, supply chains, and food available for human consumption.

In 2013, the global average per capita energy availability from vegetal products was 2370 kilocalories per person per day, and 514kcal from animal products. Animal products therefore accounted for [514 / (514 + 2370) * 100] = 18% of the world’s calories.

The global average per capita protein availability from vegetal products was 49 grams per person per day, and 32g from animal products. Animal products therefore accounted for [32 / (32 + 49) * 100] = 39% of the world’s protein.

The figures given here are slightly lower for protein production (37% of the world total) because seafood from wild capture fisheries are not included (as they are not grown on terrestrial land).
The number of species evaluated and threatened with extinction on the IUCN Red List is available from their summary statistics found here. In 2019, 28,338 were listed as threatened with extinction. Species can be filtered by threat categories in the IUCN’s search function here. In 2019, 24,001 species were threatened by ‘agriculture and aquaculture’. Note that species can have multiple threats; this therefore does not mean agriculture was the only threat for such species.
Poore, J., & Nemecek, T. (2018). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392), 987-992.
IPCC, 2014: Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. IPCC, Geneva, Switzerland, 151 pp.
Poore, J., & Nemecek, T. (2018). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392), 987-992.
6% of land use change results from conversion from food for human consumption, and 12% for the production of animal feed. Savannah burning (2% of food emissions) is largely burning of bush land in Africa to allow animal grazing. Emissions from cultivated organic soils (4%) are split between human food and animal feed. This is where very high carbon soils are used for cropland, and this releases carbon. It’s a major issue in palm plantations and also in some Northern Hemisphere countries.

This means food for direct human consumption is equal to 6% (land use change) + 2% cultivated soils = 8%
Livestock is equal to 12% (land use change) + 2% savannah burning + 2% cultivated soils = 16%.
Gustavsson, G., Cederberg, C., Sonesson, U., Emanuelsson, A. (2013). The methodology of the FAO study: ‘Global food losses and food waste—extent, causes and prevention’ – FAO, 2011. Swedish Institute for Food and Biotechnology (SIK) report 857, SIK.
The 2018 Pew Research Center Survey polled people across the world on global threats: in many countries more than 8-in-10 people said that climate change was a major threat to their country. Even in countries which showed less concern, a large percentage saw it as a major threat: 59% in the US said it was a serious threat.
This was a marked increase in concern from similar polls conducted a few years earlier.
Poore, J., & Nemecek, T. (2018). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392), 987-992.
To express all greenhouse gases in carbon dioxide equivalents (CO2-eq), they are each weighted by their global warming potential (GWP) value. GWP measures the relative warming impact one molecule or unit mass of a greenhouse gas relative to carbon dioxide over a given timescale – usually over 100 years. For example, one tonne of methane would have 34 times the warming impact of tonne of carbon dioxide over a 100-year period. GWP100 values are used to combine greenhouse gases into a single metric of emissions called carbon dioxide equivalents (CO2e). CO2e is then derived by multiplying the mass of emissions of a specific greenhouse gas by its equivalent GWP100 factor. The sum of all gases in their CO2e form provide a measure of total greenhouse gas emissions.
Sandström, V., Valin, H., Krisztin, T., Havlík, P., Herrero, M., & Kastner, T. (2018). The role of trade in the greenhouse gas footprints of EU diets. Global Food Security, 19, 48-55.
Weber, C. L., & Matthews, H. S. (2008). Food-miles and the relative climate impacts of food choices in the United States. Environmental Science & Technology.
This figure is very similar to the previous estimates we looked at from Joseph Poore and Thomas Nemecek (2018) where transport accounted for 6% of emissions.
Hospido, A., i Canals, L. M., McLaren, S., Truninger, M., Edwards-Jones, G., & Clift, R. (2009). The role of seasonality in lettuce consumption: a case study of environmental and social aspects. The International Journal of Life Cycle Assessment, 14(5), 381-391.
Carlsson-Kanyama, A., Ekström, M. P., & Shanahan, H. (2003). Food and life cycle energy inputs: consequences of diet and ways to increase efficiency. Ecological Economics, 44(2-3), 293-307.
’Food miles’ are measured in tonne-kilometers which represents the transport of one tonne of goods by a given transport mode (road, rail, air, sea, inland waterways, pipeline etc.) over a distance of one kilometre. Poore & Nemecek (2018) report that of the 9.4 billion tonne-kilometers of global food transport, air-freight accounted for only 15 million. This works out at only 0.16% of the total; most foods are transported by boat.
Temperature-controlled transport by sea generates 23g CO2eq per tonne kilometer, whereas temperature controlled air transport generates 1130g CO2eq per tonne kilometer.
We get this footprint value as: [9000km * 0.023kg per tonne-kilometer / 1000 = 0.207kg CO2eq per kg].
The average footprint of avocados is around 2.5kg CO2eq per kg.
The mean emissions from beef very much depend on whether it’s sourced from dairy herds or from dedicated beef herds. Beef from dairy herds tends to have a lower footprint since its footprint is essentially ‘shared’ with dairy co-products. The mean footprint of beef from dairy herds is 17 kgCO2eq; from dedicated beef herds it’s 50 kgCO2eq. Around 56% of global beef production comes from dedicated beef herds; and 44% from dairy herds. The mean footprint is approximately 35 kgCO2eq [56% * 50 + 44% *17 = 35 kgCO2eq]. Note that if you use the median footprint, this figure is 25 kgCO2eq – more than 60 times higher than peas.
Poore, J., & Nemecek, T. (2018). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392), 987-992.
CO2 is the most important GHG, but not the only one – agriculture is a large source of the greenhouse gases methane and nitrous oxide. To capture all GHG emissions from food production researchers therefore express them in kilograms of ‘carbon dioxide equivalents’.

To express all greenhouse gases in carbon dioxide equivalents (CO2-eq), they are each weighted by their global warming potential (GWP) value. GWP measures the relative warming impact one molecule or unit mass of a greenhouse gas relative to carbon dioxide over a given timescale – usually over 100 years. GWP100 values are used to combine greenhouse gases into a single metric of emissions called carbon dioxide equivalents (CO2eq). CO2eq is then derived by multiplying the mass of emissions of a specific greenhouse gas by its equivalent GWP100 factor. The sum of all gases in their CO2eq form provide a measure of total greenhouse gas emissions.
This 25 kgCO2eq figure represents the median emissions from beef production. You might notice that this is lower than our earlier figure of 35 kgCO2eq – this represents the mean emissions from beef. Because of the skew in production – a small number of producers create most impact – the mean and median values can be quite different.
Here, by ‘largest impact’ I have taken the 90th percentile value. This means that 90% of global pea, tofu or nut production has a carbon footprint less than this figure.
Here, by ‘lowest impact’ I have taken the 10th percentile value. This means that only 10% of global production has a carbon footprint below this figure.
The European Environment Agency reports that the EU’s total greenhouse gas emissions in 2017 were approximately 4.5 billion tonnes of carbon dioxide equivalents.
MacLeod, M., Gerber, P., Mottet, A., Tempio, G., Falcucci, A., Opio, C., Vellinga, T., Henderson, B. & Steinfeld, H. (2013). Greenhouse gas emissions from pig and chicken supply chains – A global life cycle assessment. Food and Agriculture Organization of the United Nations (FAO), Rome.
German, R. N., Thompson, C. E., & Benton, T. G. (2017). Relationships among multiple aspects of agriculture’s environmental impact and productivity: a meta‐analysis to guide sustainable agriculture. Biological Reviews, 92(2), 716-738.
Gerber, H. Steinfeld, B. Henderson, A. Mottet, C. Opio, J. Dijkman, A. Falcucci, G. Tempio, “Tackling climate change through livestock: A global assessment of emissions and mitigation opportunities” (FAO, 2013).
Sandström, V., Valin, H., Krisztin, T., Havlík, P., Herrero, M., & Kastner, T. (2018). The role of trade in the greenhouse gas footprints of EU diets. Global Food Security, 19, 48-55.
Due to data availability on trade flows and national emission factors for fish and other seafood were not included in this analysis. The authors note that the items included in the analysis accounted for approximately 95% of energy intake in EU diets.
Crippa, M., Solazzo, E., Guizzardi, D. et al. Food systems are responsible for a third of global anthropogenic GHG emissions. Nature Food (2021).
Poore, J., & Nemecek, T. (2018). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392), 987-992.
You might think that this figure of 6% is strongly dependent on where in the world you live – that if you live somewhere very remote, that the role of transport must be much higher. But this is not really the case.

Let’s take the example of beef from a beef herd. The average footprint of this beef is approximately 60 kilograms of CO2eq per kilogram of beef. Let’s compare the transport footprint of buying from your local farmer (who lives just down the road from you), versus someone in the UK transporting beef from Central America (approximately 9000 kilometers away).

Transporting food by boat emits 0.023 kilograms of CO2eq per tonne of product per kilometer. To transport the 9000 kilometers from Central America to the UK therefore emits 0.207 kilograms CO2eq [9000km * 0.023kg per tonne-kilometer / 1000 = 0.207 kg CO2eq per kg]. This is only equivalent to 0.35% of the total footprint of the 60 kilograms of CO2eq per kilogram of beef.
If you buy from your local farmer – let’s assume you walk there, and have zero transport emissions – your beef footprint is 59.8 kilograms CO2eq per kilogram [we calculate this as 60kg – 0.2kg]. It makes almost no difference.
Especially for foods with a large footprint, transport as a share of the food’s total emissions is fairly insensitive to the distance travelled.
These emissions factors by transport mode are those applied in the analysis by Joseph Poore and Thomas Nemecek (2018), published in Science. These emission factors are sourced from Ecoinvent v3.3, a comprehensive database which is commonly used in international life-cycle analyses (LCA). Emission factors can span a range of values depending on factors such as the efficiency of vehicle used; packing/loading density of freight; distribution between passenger and freight allocation in shared transport; amongst other factors.
Poore, J., & Nemecek, T. (2018). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392), 987-992.
Searchinger, T. et al. (2018). Creating a Sustainable Food Future—A Menu of Solutions to Feed Nearly 10 Billion People by 2050. World Resources Institute.
Poore, J., & Nemecek, T. (2018). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392), 987-992.
Food production is responsible for 26% of global greenhouse gas emissions; and food waste is responsible for 24% of that figure. Therefore food waste as a share of global emissions is [24% * 26% = 6%].
Latest data from the World Resource Institute’s CAIT Climate Data Explorer reports that aviation accounts for 1.9% of global greenhouse gas emissions. Food losses and waste accounts for around 6% – around three times the share from aviation. You can explore emissions by sector from the World Resources Institute here.
This comparison of food waste and countries is now common, and sometimes criticised for the fact that it double-counts emissions.We’re comparing food waste with country emissions without accounting for the fact that these ‘food waste’ emissions are also included in national emissions figures. To make this accurate, the emissions of each country should be slightly lower than their reported values because we should remove the emissions from food waste for each.

This is a valid criticism. However, even if we were to remove food waste emissions from each country’s total, this ranking would remain the same. Food waste would not fall down the rankings since its 4th placed competitor – India – would see a slight drop in emissions. And it’s not possible that it would overtake the United States or China; the amount of emissions therefore allocated to food waste would be much smaller than the current gap.

If we accounted for this double-counting, the rankings would stay the same.
The food system and losses data in the study by Poore and Nemecek (2018) relates to the year 2010. Emissions from food losses and waste were 3.3 billion tonnes of carbon-dioxide equivalents (CO2eq) – 2.1 GtCO2eq from supply chain losses, and 1.2 GtCO2eq from consumer waste.
The World Resource Institute’s CAIT Climate Data Explorer reports that in 2010, the top three emitters were China (9.8 GtCO2eq; 21%); the USA (6.1 GtCO2eq; 13%) and India (2.5 GtCO2eq; 5.3%). Food waste would therefore lie between the USA and India.
Sandström, V., Valin, H., Krisztin, T., Havlík, P., Herrero, M., & Kastner, T. (2018). The role of trade in the greenhouse gas footprints of EU diets. Global Food Security, 19, 48-55.
Despite a large share of the population saying they now drink plant-based alternatives, dairy milk still dominates the UK market in terms of sales volume (with 96% for white milk). Market surveys suggest people favor cow’s milk versus vegan milks for particular uses e.g. hot versus cold drinks.
This data comes from the largest meta-analysis of food impacts to date, published by Joseph Poore and Thomas Nemecek (2018) in Science. In this study, the authors looked at data across more than 38,000 commercial farms in 119 countries and quantified their environmental impacts taking into account the entire production chain – from land-use change through to retail and packaging.
Poore, J., & Nemecek, T. (2018). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392), 987-992.
One way of comparing the quality of different protein sources is using their Protein Digestibility-Corrected Amino Acid Score (PDCAAS). This score looks not only at the total protein they provide but also digestibility, and whether there are particular deficiencies of specific amino acids. Most animal proteins tend to score very highly on PDCAAS. Plant-based foods such as soy also score very highly. But achieving a complete animo acid profile on a vegan diet requires a mix of grains, legumes and meat-free substitute proteins.

Schaafsma, G. (2000). The protein digestibility–corrected amino acid score. The Journal of Nutrition, 130(7), 1865S-1867S.

Young, V. R., & Pellett, P. L. (1994). Plant proteins in relation to human protein and amino acid nutrition. The American Journal of Clinical Nutrition, 59(5), 1203S-1212S.
Poore, J., & Nemecek, T. (2018). Reducing food’s environmental impacts through producers and consumers. Science, 360(6392), 987-992.

FAOstat: UN Food and Agriculture Organization (FAO) Statistics. Available at: http://www.fao.org/faostat/en/#data.

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