Chapter 1. Global agroclimatic patterns

Chapter 1 describes the CropWatch Agroclimatic Indicators (CWAIs) rainfall (RAIN), temperature (TEMP), and radiation (RADPAR), along with the agronomic indicator for potential biomass (BIOMSS) in 105 global Monitoring and Reporting Units (MRU). RAIN, TEMP, RADPAR and BIOMSS are compared to their average value for the same period over the last fifteen years (called the “average”). Indicator values for all MRUs are included in Annex A table A.1. For more information about the MRUs and indicators, please see Annex B and online CropWatch resources at www.cropwatch.com.cn.

1.1 Introduction to CropWatch agroclimatic indicators (CWAIs)

This bulletin describes environmental and crop growth conditions over the period from January to April 2024, JFMA, referred to as "reporting period". CWAIs are averages of climatic variables over agricultural areas only inside each MRU and serve the purpose of identifying global climatic patterns. For instance, in the "Sahara to Afghan desert" MRU, only the Nile Valley and other cropped areas are considered. MRUs are listed in Annex B. Refer to Annex A for definitions and to table A.1 for JFMA numeric values of CWAIs by MRU. Although they are expressed in the same units as the corresponding climatological variables, CWAIs are spatial averages limited to agricultural land and weighted by the agricultural production potential inside each area.

We also stress that the reference period, referred to as "average" in this bulletin covers the 15-year period from 2009 to 2023. Although departures from the 2009-2023 are not anomalies (which, strictly, refer to a "normal period" of 30 years), we nevertheless use that terminology. The specific reason why CropWatch refers to the most recent 15 years is our focus on agriculture, as already mentioned in the previous paragraph. 15 years is deemed an acceptable compromise between climatological significance and agricultural significance: agriculture responds much faster to persistent climate variability than 30 years, which is a full generation. For "biological" (agronomic) indicators used in subsequent chapters we adopt an even shorter reference period of 5 years (i.e., 2019-2023). This makes provision for the fast response of markets to changes in supply.

Correlations between variables (RAIN, TEMP, RADPAR and BIOMSS) at MRU scale derive directly from climatology. For instance, the positive correlation between rainfall and temperature results from high rainfall in equatorial, i.e., in warm areas.

Considering the size of the areas covered in this section, even small departures may have dramatic effects on vegetation and agriculture due to the within-zone spatial variability of weather. It is important to note that we have adopted an improved calculation procedure of the biomass production potential in the bulletin based on previous evaluation.

1.2 Global overview

The January–April global surface temperature ranked warmest in the 175-year record. It was at 1.34°C above the 20th century average of 12.6°C. Global warming is increasingly becoming a driver of heat waves, droughts and floods. Another driver of extreme weather anomalies are ocean-atmosphere oscillations. El Niño is one of these oscillations. It is forecasted to end in the coming months. It brought drought conditions to Southeast Asia, southern Africa, Amazonia and Central America. It also caused record flooding in southern Brazil.

1.3 Rainfall

In South America, the patterns of rainfall departures from the 15YA were similar to those reported in the previous bulletin: The most severe deficit  (<-30%) was observed in the Cerrado and Mato Grosso in Brazil, both of which are important producers of soybean. In Mexico, a similar deficit was observed for the Central Highlands. The extreme drought conditions continued in the Maghreb. In southern Africa, rainfall stopped in mid-January, at the peak of what was supposed to be the rainy season. In Southeast Asia and Western Africa, the rainy season did not start on time, and hardly any rainfall has been observed so far this year in those two regions. The region along the equator in South America, including the Amazon basin and the Andes from Bolivia to Columbia and Central America, Central Africa, most of the Mediterranean Basin, and the Himalayas and Tibetan Plateau, the Indo-Gangetic plains as well as north-east Siberia experienced a rainfall deficit in the range of -30 to -10%. Argentina and Chile had average to above-average rainfall, and so did North America, with the exception of the above-mentioned Mexican Highlands. Most of Central and Eastern Europe, and Central Asia had average rainfall. Central and Eastern China, as well as Mongolia and Indonesia, had positive rainfall departures exceeding 30%.

Figure 1.1 Global map of rainfall anomaly (as indicated by the RAIN indicator) by CropWatch Mapping and Reporting Unit: Departure of January to April 2024 total from 2009-2023 average (15YA), in percent.

1.4 Temperatures

There was only one region that reported negative temperature departures: New Zealand, where average temperatures were more than 0.5ºC below the 15YA. Temperatures stayed at average levels in South America along the Pacific Coast, as well as in the Western USA, the regions bordering the Arctic in Europe and Russia, as well as in the Hindukush and Himalayan regions. In all other regions, average temperatures were at least 0.5ºC warmer than the 15YA. The strongest departures, exceeding +1.5ºC, were observed for the Amazon basin, the Midwest and Northeast of the USA, the Mediterranean Basin, Eastern Europe, the Levant, the Koreas, Japan, Vietnam, and southern Africa.

Figure 1.2 Global map of temperature anomaly (as indicated by the TEMP indicator) by CropWatch Mapping and Reporting , Unit: departure of January to April 2024 average from 2009-2023 average (15YA), in °C.

1.5 RADPAR

Photosynthetically active solar radiation was rather variable within continents. In all crop producing regions of Argentina, Paraguay, Uruguay and Parana in Brazil, as well as northern Chile and coastal Peru, and most of North America, solar radiation was below the 15YA by more than 3%. Similar departures were observed for Central and Eastern Europe, Siberia, Eastern China, the Koreas, Japan and Indonesia. To the contrary, solar radiation was by more than 3% above the 15YA in Central America, southern Africa, the Mediterranean Basin, and most of southeast Asia and western Australia. Central Brazil as well as East Africa and most of India experienced average solar radiation levels.

Figure 1.3 Global map of photosynthetically active radiation anomaly (as indicated by the RADPAR indicator) by CropWatch Mapping and Reporting Unit: departure of January to April 2024 average from 2009-2023 average (15YA), in percent.

1.6 BIOMSS

Biomass is estimated as a function of rainfall, temperature and solar radiation. Thanks to the above average rainfall, positive departures from the 15YA by more than +5% were estimated for the coastal zone of Peru, the west coast of North America, most of the USA, Central and Eastern Europe as well as East Asia. The largest reductions in biomass production by more than -5% were estimated for southeast Asia, the Gangetic Plains, most of West, Central and South Africa, the Maghreb, Central America, Central Brazil, and Western Australia.

Figure 1.4 Global map of biomass accumulation (as indicated by the BIOMSS indicator) by CropWatch Mapping and Reporting Unit: departure of January to April 2024 average from 2009-2023 average (15YA), in percent