Projection of Thermal Bioclimate of Egypt for the Paris Agreement Goals

Abstract

This paper presents the likely changes in the thermal bioclimate of Egypt under the Paris Agreement, which aimed to restrict global warming to increase by 1.5–2.0 °C. A mean multi-model ensemble (MME) of eight global climate models were employed to evaluate the two shared socioeconomic paths (SSP) scenarios SSP1-1.9 and SSP1-2.6, which indicated scenarios for 1.5 and 2.0 °C rates of warming, respectively. The spatial distribution of the observed bioclimate indicated higher values in the south and southeast regions. The findings showed that there was an increase in Egypt’s mean temperature by rates of 1.3 and 1.5 °C for SSP1-1.9 and SSP1-2.6, respectively, with a higher increase in the southeast. The SSP1-2.6 scenario showed a gradual temperature rise with time, while SSP1-1.9 projected a decrease in the far future. The daily temperature variation decreased in the same region, but this effect was amplified in the north by 0.2 °C. The seasonality decreased by −0.8 to −2.3% without any shift in isothermality. The maximum summer temperature increased more (1.3–2.2 °C) than the minimum winter temperature (0.9–1.5 °C), causing an increase in inter-seasonal variability. Most bioclimatic indicators more rapidly rose in the north and northeast regions of Egypt, according to the geographical distribution of their projections.

1. Introduction

A bioclimate affects a region’s species distribution, plant cover, ecology, irrigation requirements, and vulnerability to climate hazards, among other factors [1,2]. As a result, understanding the bioclimate of a region is valuable for understanding how climate affects living creatures on an annual and seasonal basis [3]. This information includes the mean values, standard deviations, inter- and intra-annual variability, and seasonality of the thermal environment. Climate factors such as temperature, humidity, and wind speed significantly affect human comfort and energy levels [4,5]. Consequently, mapping the spread of human comfort zones using thermal bioclimatic indicators provides valuable information [6,7]. The indicators can help assess a region’s suitability for cultivating a specific crop type [8].

Many climatic features associated with a biosphere have shifted due to climate change [9,10,11]. The bioclimate is sensitive to minor changes in the climate; therefore, climate change can significantly affect the biological distribution [12,13,14,15]. It may also lead to a change in the species distribution and ecology of a region [16,17]. Climate changes affect many climate variables (e.g., temperatures, precipitations, etc.) and their characteristics, such as seasonality and intra-annul variability [4,18,19]. These have also altered the environmental risks to human health and the biological habitat. Therefore, bioclimatic indicators have been increasingly assessed to understand climate change effects on bioenvironments [20,21,22]. Knowing the changes in bioclimate is also quite beneficial for climate change adaptation and sustainable bioenvironment management [11,23].

Human-caused greenhouse gases (GHG) emissions and land-use changes will continue to impact climate in the future. Simulating Earth’s climatic reaction to GHG emissions and land-use changes requires global climate models (GCMs) [24,25,26]. These GCMs are being released as part of the phases of the Coupled Model Intercomparison Project (CMIP). The most recent project (CMIP6) differs from previous CMIPs as it incorporates much more reliable Earth processes [27,28]. Moreover, the models project climate for different scenarios that are labelled as shared socioeconomic pathways (SSPs). Two SSPs (SSP1-1.9 and SSP1-2.6) address the Paris Agreement’s goals of controlling global warming to only a 1.5 and 2.0 °C increase above the pre-industrial era [29,30]. SSP1-1.9 demonstrates the scenario where CO₂ emissions would net zero around 2050, which is the most optimistic scenario. This transition caused a shift in societal attention from economic growth to total well-being. This scenario would limit warming to around 1.5 °C above pre-industrial, dipping back to 1.4 °C by 2100. SSP1-2.6 is the second most optimistic scenario, which projects CO₂ emission reduction at a slower rate than in SSP1-1.9; it projects a steady rise in global warming until it reaches 1.8 °C by 2100.

Egypt has a unique biogeographical characteristic due to its location at the heart of the great Saharo-Sindian desert belt. It is also the intersection of four biogeographical regions: the Mediterranean, Afrotropical, Irano-Turanian, and Saharo-Sindian. In addition, it includes six biogeographical sectors (Figure 1), including the Libo-Nubian, Nilotic, Marioutico-Arishian, Sinaico-Arabian, Elbanian, and Suezian sectors [31]. Additionally, the Nile River penetrates the country from south to north. The Red Sea and Mediterranean Sea are linked by the Suez Canal, which has a long-term impact on the biotic diversity [32,33,34]. Egypt is home to highly diverse terrestrial habitats, flora, and fauna compositions. However, due to the arid and hyper-arid climates, a few species with some endemic species can be found [35,36]. Recent changes in land-use [37], pollutants [38,39], and human activities [40,41] have affected the biodiversity of several locations in Egypt.

This study aims to quantify the bioclimate change in Egypt over time for the most optimistic scenarios of limiting global warming according to the Paris Agreement. Eleven thermal bioclimatic indicators were projected for SSP1-1.9 and SSP1-2.6 using eight CMIP6 GCMs. The projections of the bioclimates would help ecologists and biologists to extend the research on climate change responses to species. Furthermore, it can aid policymakers in formulating climate change mitigation and adaptation policies for Egypt.

2. Research Area and Climate Data

2.1. Egypt

Egypt (21.7° N–31.7° N and 24.7° E–35.8° E) is a northeast African country with a population above 100 million and an area of approximately one million km². Egypt’s terrain is almost flat, excluding the eastern Red Sea and Sinai Mountains, northern Qattara Depression, and southwestern Al Jelf Alkabir Plateau (Figure 1). Egypt has an arid climate with an annual precipitation of nearly 200 mm in the north and below 5 mm in the southern desert, respectively [42,43]. The average Tmax and Tmin are 27.7 and 15.8 °C; the south is relatively hotter than the north.

2.2. Climate Data

This study employed CMIP6 GCMs to evaluate the likely changes in the thermal bioclimates of Egypt. Eight different GCMs were used, and are listed in the first table (Table S1) in Supplementary Materials. They all shared a common initial variant label, r1i1p1f1. The outputs of the GCMs (e.g., monthly accumulative precipitation and monthly mean Tmax and Tmin) that were used were the historical (1975–2014) and future simulations (2020–2099) under SSP1-1.9 and SSP1-2.6, which address the Paris Agreement’s goal. SSP1-1.9 simulates the climate considering a global warming of lower than 1.5 °C at 2100, following a mild increase (1.6 °C) at the mid-century. This scenario utilizes SSP1, which models a sustainable choice for Earth’s future development; it represents the most optimistic scenario. SSP1-2.6 shares the same SSP, but has higher Representative Concentration Pathways (RCP) (2.6 W/m²) that considers global warming being limited to 1.8 °C at the end of the century. To eliminate any potential for bias in geographical representation, the results of both the historical and future GCMs were interpolated to a resolution of 100 km × 100 km.

3. Methodology

The climatic and bioclimatic changes are very diverse among locations. The fast increase in global temperature mainly affects the thermal bioclimates. Consequently, thermal indicator changes must be urgently addressed. Climate change may be more effectively monitored using bioclimatic markers. In light of the global warming objectives established by the Paris Agreement, our analysis assessed how the future thermal bioclimatic indices in Egypt will shift. Eleven thermal bioclimatic indicators (Table S2 in Supplementary Materials) were adopted to address this aim, as listed in the Results subsections.

Bioclimatic indicators were computed using the climatic variables (rainfall, Tmax, and Tmin) derived from the GCM simulations. The eight GCM outputs were used to create a mean MME, which was utilized to calculate the bioclimatic indicators for the historical (1975–2014) and two future periods, near (2020–2059) and far (2060–2099). Each thermal bioclimatic indicator’s historical status was presented using the respective MME mean. The projected changes in the MME in the two future periods compared with the historical MME were computed to show the spatial distributions of the changes. The primary goal of the MME mean is to reduce uncertainty in future simulations and accurately represent climate change [44,45,46]. The changes in bioclimatic indicators were calculated at each grid to create maps of the projected changes in the indicators for different periods.

4. Results

4.1. Annual Mean Temperature (Bio-1)

Figure 2 shows the Bio-1 distribution in Egypt. The Bio-1 ranged between 20.5 °C in the northwest and 24.5 °C in the southeast. There is a steady rise in the mean temperature (Tmean) from the north to the south. The projections of Bio-1 showed a rise of 1.1–1.7 °C. The projected near future change ranged between 1.2 °C and 1.6 °C; in the 2060–2099 range, the increase was projected to be between 1.1 and 1.7 °C. The changes are lower during the 2060–2099 period compared with the 2020–2059 range for the SSP1-1.9 scenario. In contrast, the changes are higher for the 2060–2099 range compared with the 2020–2059 range for the SSP1-2.6 scenario.

4.2. Diurnal Temperature Range (Bio-2)

Bio-2 is the daily variation between the Tmax and Tmin, which significantly impacts ecosystems. The lesser influence of the local climate on Bio-2 has made it a good indicator of climate change for global warming [47]. According to some research, Tmin has significantly increased above Tmax, decreasing the Bio-2 in various places [47,48]. On a global scale, this phenomenon has been linked to climate change. The Bio-2 (Figure 3) of Egypt showed a wide variation across the region, ranging from 6.0 to 19.0 °C. However, the projected changes of this indicator were very low, ranging between −0.1 °C and 0.2 °C. The changes were positive in the north and negative in the south for both SSPs. The increase was larger in the far future, particularly in the northern regions.

4.3. Isothermality (Bio-3)

Bio-3 is regarded as an essential indicator in tropical and coastal locations as it is the proportion of Bio-2 (daytime temperature spread) to Bio-7 (yearly temperature spread) [49]. A low Bio-3 value suggests a lesser variability in the daily temperature than in the yearly; it can range from 0 to 100%. Figure 4 depicts the geographical variability of Bio-3 in Egypt during the reference period, along with the shifts for the future periods. The Bio-3 ranged between 31.0 and 44.0% in Egypt. The lowest values were found in the coastal regions, especially along the Red Sea. The Bio-3 was projected to decrease for both scenario models and future periods. However, the change would be very small (0 to −0.7%), indicating a minimal influence of climate change on isothermality. Additionally, the changes were projected to be lower for the far future period, indicating no change in isothermality if global warming can be limited according to the Paris Agreement.

4.4. Temperature Seasonality (Bio-4)

Figure 5 describes the geographical variability of the historical and future shifts in Bio-4 across Egypt. The greater the seasonality, the greater the percentage change in temperature over a year, indicating a greater temperature fluctuation, and vice versa [3]. The Bio-4 ranged between 26.0% in the southeast and 39.0% in the northeast. The analysis showed that the future changes ranged between −0.8 and −2.3% for the different SSPs and periods. The average deviations were −1.3 and −1.7% for SSP1-1.9 and 1-2.6, respectively. The region with the lower Bio-4 will likely experience a smaller shift and vice versa for both SSPs. This indicates the future spatial heterogeneity in Bio-4 due to climate change.

4.5. Tmax in the Hottest Month (Bio-5)

Figure 6 depicts the warmest monthly temperature (Bio-5) for Egypt’s historical and climate change scenarios. The Bio-5 varied between 36.0 and 43.0 °C. The minimum was in the Mediterranean (36.5 °C) region, while the highest value was in the southeast region. The temperature rise was projected to increase between 1.3 and 2.2 °C for the SSPs. The shifts were projected to be lowest for SSP1-1.9 during the 2060–2099 period, with an average of 1.3 °C, while the shift was highest (1.9 °C) for the SSP1-2.6 scenario during the 2060–2099 period.

4.6. Tmin in the Coldest Month (Bio-6)

Figure 7 presents the present status and projections of the Tmin in the coldest month (Bio-6). The Bio-6 in Egypt varied from 3.5 in the southwest to 9.0 °C along the Red Sea coast. Both SSPs showed the future temperatures rising between 0.9 and 1.5 °C. The increase for SSP1-2.6 was predicted to be more than SSP1-1.9 in both future periods. The greatest change was observed for SSP1-2.6 in 2060–2099 (1.0 °C), while the smallest change was observed for SSP1-1.9 in 2060–2099 (1.5 °C).

4.7. Annual Range of Temperature (Bio-7)

Bio-7 is the subtraction of Bio-6 from Bio-5. Figure 8 depicts the historical and future changes in Bio-7 in Egypt. The Figure shows that Bio-7 varied between 26.0 and 34.0 °C. The Bio-5 in most study areas was more than 33 °C, while it was low in the coastal regions. The likely shift in Bio-7 was projected to be between 0.3 and 0.4 °C. The greatest changes were observed in northeast Egypt, and the least change was observed in the south for both scenarios.

4.8. Tmean of the Wettest Quarter (Bio-8)

Due to the large diversity of Egypt’s climate, the wettest quarter experiences large swings in precipitation. The wettest three months at each location were identified from the total precipitation for three successive months. Figure 9 depicts the Tmean during the wettest quarter. The Bio-8 increased from north (16 °C) to south (24 °C). Future projections showed an uneven distribution in the change in Bio-8 across the study area for both SSPs. The increase in the Tmean was projected to be 1.5 °C for SSP1-1.9 in 2020–2059 and 1.3 °C in 2060–2099. For SSP1-2.6, the Tmean was projected to rise by 1.8 °C in 2020–2059 and by 2.2 °C in 2060–2099.

4.9. Tmean of the Driest Quarter (Bio-9)

The precipitation of three successive months was calculated in each location to find the driest period. Figure 10 illustrates the geographical variability of Bio-9 for the historical period and its likely changes for the two SSPs. The highest Bio-9 occurred in the middle and north regions (>28.5 °C), and the lowest occurred in the southwest (nearly 16.0 °C). The mean future change in Bio-9 was projected to be 1.1 °C and 1.4 °C for SSP1-1.9 and 1-2.6, respectively, representative of the 2060–2099 period. The lowest increase in Bio-9 was projected to occur in the Red Sea region, which increased by 0.2 °C for both SSPs in the 2060–2099 period. The northern part experienced the largest rise (>2 °C) for both scenarios.

4.10. Tmean of the Warmest Quarter (Bio-10)

The Tmean for three successive months was computed to find the warmest quarter in each location. Figure 11 presents the geographical variability in Bio-10 and its future changes for the SSPs. The Bio-10 in Egypt varied between 27.0 and 33.0 °C. The Bio-10 was the greatest in the southeast and the least in the Mediterranean areas. It was projected to rise between 1.3 and 1.7 °C in the 2020–2059 period and between 1.2 and 1.5 °C in the far future period for SSP1-1.9. The mean change in Bio-10 for SSP1-2.6 was 1.7 and 1.9 °C in the 2020–2059 and 2060–2099 periods, respectively, meaning a higher rise in Bio-10 for the SSP1-2.6 scenario than SSP1-1.9 and a higher rise in 2060–2099 compared with 2020–2059.

4.11. Tmean of the Coldest Quarter (Bio-11)

Figure 12 presents the geographical variability of Bio-11 for the historical period and its shifts in the two future periods for both SSPs. The Bio-11 ranged between 9.7 and 19.7 °C in Egypt. The lowest Bio-11 was in the northeast, and the highest was observed in the southeast. The Bio-11 was projected to rise for both SSPs and future periods. The lowest mean increase was projected in 2060–2099 for SSP1-1.9 (1.0 °C). In contrast, the largest rise in the mean Bio-11 was projected in 2060–2099 for SSP1-2.6 (1.2 °C). The maximum change (>1.6 °C) was projected in the east of the study area for SSP1-2.6 in 2060–2099. The Bio-11 was projected to have a smaller increase than Bio-10, indicating more annual variation in the temperature between the coldest and warmest quarters.

5. Discussion

The future changes of the eleven thermal bioclimatic indicators in Egypt were presented in this study. The projections were made using the MME means prepared from eight CMIP6 GCMs and the Tmax, Tmin, and precipitation for SSP1-1.9 and 1-2.6. They represent the Paris Agreement’s goals of limiting the mean global warming to 1.5 and 2.0 °C. The projected future values of the indicators were compared with the reference period to calculate their possible shifts in two future periods. This provided the likely response of the indicators to the short- and long-term changes in the global mean temperature. An increased sensitiveness of the bioenvironment to climate change was observed over the entire research region, as shown by the geographical variability of the shifts for several biothermal indicators (

Table 1. Summary of the results of the bioclimatic projection.

Indicator	Change
	Increase	Decrease
Bio-1	Entire study area. A higher increase was projected for SSP1-2.6 in 2060–2099.	-
Bio-2	North region. A higher increase was projected in the northeast.	South region. A higher decrease was projected in the southwest.
Bio-3	-	All over the study area. The southwest has a greater projected decline.
Bio-4	-	All over the study area, with a greater decline projected in the northeast
Bio-5	All over the study area, with a greater increase projected in the northeast	-
Bio-6	All over the study area. The south and southeast have a higher projected increase.	-
Bio-7	All over the study area. The north has a higher projected increase.	-
Bio-8	All over the study area. A higher increase was projected in the east (Red Sea).	-
Bio-9	All over the study area. The north has a higher projected increase.	Red Sea region
Bio-10	All over the study area	-
Bio-11	All over the study area. The southeast has a higher projected increase.	-

). Although the Paris Agreement shows that reducing carbon emissions may considerably lessen climate change’s harmful consequences [50], several of the future bioclimatic indicators in Egypt would significantly change even if the goal is achieved. The high values of the bioclimatic indicators were mostly observed in the south and southeast regions of Egypt for the reference period. This indicates that the region is highly vulnerable to temperature-related extremes. The future projections showed different distributions in the change of different indicators. On the other hand, most indicators showed the greatest increase in Egypt’s northern and northeastern regions. For SSP1-1.9, a rise of 1.3 °C in the annual mean temperature was projected; for SSP1-2.6, an increase of 1.5 °C was projected, notably in the southeast region of Egypt. The daily temperature variance was expected to decrease in the southeast region while increasing in the north by 0.2 °C. The hot season maximum temperatures rose by 1.3–2.2 °C, whereas the winter minimum temperatures rose by 0.9–1.5 °C.

This study showed that there was a higher increase in the temperature in MENA during the hottest quarter/month compared with the coldest quarter/month. These phenomena caused an increase in the annual temperature range and variations in other thermal bioclimatic indicators in the region. Cloud-free and hot weather conditions prevail in the summer of the region [51]. The elevated greenhouse gases enhance the downward component of the longwave flux, which is particularly relevant under clear skies [52]. Therefore, the temperature in the hottest month or quarter is projected to increase more in MENA than the coldest month/quarter.

Regional temperature change is often associated with evaporation, which contributes to surface cooling [53]. However, this is not the case for arid MENA regions due to the low soil heat storage capacity. The surface heat budget in an arid region is primarily controlled by radiative cooling [54]. There is more cloud cover in the northern Mediterranean coastal region, particularly in the elevated northeastern region of Egypt. These conditions reduced the surface radiative cooling and contributed to a higher regional climate warming. The greater increase in the hottest month/quarter temperature caused a greater increase in most bioclimatic indicators in the north and northeast compared with other parts of Egypt.

The majority of economic activities in Egypt are concentrated in the north. Almost all of the population also reside in the north. The spatial pattern of the projected shifts of the bioclimates showed a higher increase in most of the indicators in the north and northeast of Egypt. The increase in temperature and greater changes in the other thermal bioclimatic indicators would affect a vast population and economy.

Few studies have projected the change in thermal bioclimatic indicators using CMIP5 GCMs [55,56,57]. However, none of them have inspected the changes in Egypt. Thus, comparing the results obtained in this study with others is difficult. Recently, Nashwan and Shahid [58] used an MME of CMIP5 GCMs, which showed that the Tmax rose by 1.6–4.2 °C for RCP4.5 and RCP8.5 in Egypt. In contrast, the Tmin rose by 1.3–4.4 °C. Moreover, the projected temperature rise in the cold month/season was higher than the hot month/season in Egypt [59].

The results showed a greater change in the near future period for SSP1-1.9 than the far future period for the different indicators. This is due to the integral core of the SSP1-1.9 scenario, which estimated a slight overshoot in temperature (1.6 °C) in 2050 [60]. However, reducing emissions would cool the Earth and limit global warming to roughly 1.4 °C by 2100 compared with the 1850–1900 period. Simultaneously, SSP1-2.6 showed global warming limits of about 1.8 °C [60]. The 20-year global Tmean changes and other evidence were used to show that global warming will reach 1.5 °C by 2025–2044 and 2023–2042 for the SSP1-2.6 and SSP1-1.9 scenarios, respectively [61]. The purpose of this article was to explain how the thermal bioclimatic indicators would change if the net-zero CO₂ emissions were achieved by the middle of the century in line with the Paris Agreement.

6. Conclusions

This study was conducted to examine how the regional thermal bioclimatic indicators would respond to limiting global warming by 1.5 and 2.0 °C by the end of the century compared with the pre-industrial era, according to the Paris Agreement’s goals. Several GCM outputs were integrated into a mean multi-model ensemble (MME) using two shared socioeconomic paths (SSPs) (SSP1-1.9 and SSP1-2.6), which addresses the efforts made to reduce CO₂ and greenhouse gases to achieve the desired goals. The GCM MME projected diverse changes in different thermal indicators, which may affect Egypt’s terrestrial habitats, flora, and fauna compositions. The ecological niche of many species is significantly limited; therefore, the shifts in the thermal bioclimatic indicators may have acute influences on Egyptian biodiversity. This is the first effort to explore the likely shift in the bioclimatic characteristics in Egypt while considering the Paris Agreement’s goals. The maps plotted in this study offer helpful bioclimate information, which could be significant for the ecological climate change adaptation planning for Egypt. This study only presented the possible mean changes in the bioclimatic indicators. In the future, the uncertainty of the projected changes can be evaluated. This study employed a limited number of GCMs due to their limited availability at the time of the study. Further work can confirm these results by including other models when they become available in the future. Furthermore, the changes in the thermal bioclimatic indicators can be explored using other SSPs.